If you do this well in advance of the need, when the need becomes real, you'll have some choices and the experiential knowledge to make some reasonable choices. Look for people who are willing to break their work down into small quantifiable tasks costing no more than what you're willing to write-off to education. Be very careful with contracts. The Termination Clause is the most important clause in any contract. Don't expect a contract with no risk.
Every business transaction involves a risk.
Just try to negotiate an equitable division of benefits and risk.