You could ask your solicitor to do judgement or bankruptcy searches against them. These cost between 30 to 60 depending on the number of results that appear. This would show up any registered judgements against the individual or if they have ever been made a bankrupt.
If there is a question of investing money ( yours), you could look for a reference from a bank manager, look for accounts in relation to previous businesses, look for guarantees or even a charge against any property they own.