fundrawtransaction "hexstring" ( options iswitness )

The fundrawtransaction RPC adds inputs to a transaction until it has enough in value to meet its out value.

*bitcoin-cli help fundrawtransaction

fundrawtransaction "hexstring" ( options iswitness )

If the transaction has no inputs, they will be automatically selected to meet its out value.
It will add at most one change output to the outputs.
No existing outputs will be modified unless "subtractFeeFromOutputs" is specified.
Note that inputs which were signed may need to be resigned after completion since in/outputs have been added.
The inputs added will not be signed, use signrawtransactionwithkey
or signrawtransactionwithwallet for that.
All existing inputs must either have their previous output transaction be in the wallet
or be in the UTXO set. Solving data must be provided for non-wallet inputs.
Note that all inputs selected must be of standard form and P2SH scripts must be
in the wallet using importaddress or addmultisigaddress (to calculate fees).
You can see whether this is the case by checking the "solvable" field in the listunspent output.
Only pay-to-pubkey, multisig, and P2SH versions thereof are currently supported for watch-only

Arguments:
1. hexstring                          (string, required) The hex string of the raw transaction
2. options                            (json object, optional) for backward compatibility: passing in a true instead of an object will result in {"includeWatching":true}
     {
       "add_inputs": bool,            (boolean, optional, default=true) For a transaction with existing inputs, automatically include more if they are not enough.
       "include_unsafe": bool,        (boolean, optional, default=false) Include inputs that are not safe to spend (unconfirmed transactions from outside keys and unconfirmed replacement transactions).
                                      Warning: the resulting transaction may become invalid if one of the unsafe inputs disappears.
                                      If that happens, you will need to fund the transaction with different inputs and republish it.
       "changeAddress": "str",        (string, optional, default=automatic) The bitcoin address to receive the change
       "changePosition": n,           (numeric, optional, default=random) The index of the change output
       "change_type": "str",          (string, optional, default=set by -changetype) The output type to use. Only valid if changeAddress is not specified. Options are "legacy", "p2sh-segwit", "bech32", and "bech32m".
       "includeWatching": bool,       (boolean, optional, default=true for watch-only wallets, otherwise false) Also select inputs which are watch only.
                                      Only solvable inputs can be used. Watch-only destinations are solvable if the public key and/or output script was imported,
                                      e.g. with 'importpubkey' or 'importmulti' with the 'pubkeys' or 'desc' field.
       "lockUnspents": bool,          (boolean, optional, default=false) Lock selected unspent outputs
       "fee_rate": amount,            (numeric or string, optional, default=not set, fall back to wallet fee estimation) Specify a fee rate in sat/vB.
       "feeRate": amount,             (numeric or string, optional, default=not set, fall back to wallet fee estimation) Specify a fee rate in BTC/kvB.
       "subtractFeeFromOutputs": [    (json array, optional, default=[]) The integers.
                                      The fee will be equally deducted from the amount of each specified output.
                                      Those recipients will receive less bitcoins than you enter in their corresponding amount field.
                                      If no outputs are specified here, the sender pays the fee.
         vout_index,                  (numeric) The zero-based output index, before a change output is added.
         ...
       ],
       "input_weights": [             (json array, optional) Inputs and their corresponding weights
         "txid",                      (string, required) The transaction id
         vout,                        (numeric, required) The output index
         weight,                      (numeric, required) The maximum weight for this input, including the weight of the outpoint and sequence number. Note that serialized signature sizes are not guaranteed to be consistent, so the maximum DER signatures size of 73 bytes should be used when considering ECDSA signatures.Remember to convert serialized sizes to weight units when necessary.
         ...
       ],
       "conf_target": n,              (numeric, optional, default=wallet -txconfirmtarget) Confirmation target in blocks
       "estimate_mode": "str",        (string, optional, default="unset") The fee estimate mode, must be one of (case insensitive):
                                      "unset"
                                      "economical"
                                      "conservative"
       "replaceable": bool,           (boolean, optional, default=wallet default) Marks this transaction as BIP125-replaceable.
                                      Allows this transaction to be replaced by a transaction with higher fees
       "solving_data": {              (json object, optional) Keys and scripts needed for producing a final transaction with a dummy signature.
                                      Used for fee estimation during coin selection.
         "pubkeys": [                 (json array, optional, default=[]) Public keys involved in this transaction.
           "pubkey",                  (string) A public key
           ...
         ],
         "scripts": [                 (json array, optional, default=[]) Scripts involved in this transaction.
           "script",                  (string) A script
           ...
         ],
         "descriptors": [             (json array, optional, default=[]) Descriptors that provide solving data for this transaction.
           "descriptor",              (string) A descriptor
           ...
         ],
       },
     }
3. iswitness                          (boolean, optional, default=depends on heuristic tests) Whether the transaction hex is a serialized witness transaction.
                                      If iswitness is not present, heuristic tests will be used in decoding.
                                      If true, only witness deserialization will be tried.
                                      If false, only non-witness deserialization will be tried.
                                      This boolean should reflect whether the transaction has inputs
                                      (e.g. fully valid, or on-chain transactions), if known by the caller.

Result:
{                     (json object)
  "hex" : "hex",      (string) The resulting raw transaction (hex-encoded string)
  "fee" : n,          (numeric) Fee in BTC the resulting transaction pays
  "changepos" : n     (numeric) The position of the added change output, or -1
}

Examples:

Create a transaction with no inputs
> bitcoin-cli createrawtransaction "[]" "{\"myaddress\":0.01}"

Add sufficient unsigned inputs to meet the output value
> bitcoin-cli fundrawtransaction "rawtransactionhex"

Sign the transaction
> bitcoin-cli signrawtransactionwithwallet "fundedtransactionhex"

Send the transaction
> bitcoin-cli sendrawtransaction "signedtransactionhex"