Hi,
I assume you are not in a relationship with your friend... therefore a BFA (Binding Financial Agreement - or pre-nup) is probably the wrong type of document for the proposed transaction.
Question - is it a loan? or the purchase of an interest in the property? what do you mean by "join title"?
If it is a loan - you will want a loan agreement setting down the terms of the loan, and a registered mortgage.over the property as security.
If it is the purchase of an interest in the property, a Contract of Sale for a partial share in the property, would be the starting point, followed by a Co-Ownership Agreement, to determine in advance how everything is going to work - exit clauses for one co-owner to sell out their share to the other, financial contributions, what happens when maintenance is required, decisions about living in the property, or renting it out, what happens if one co-owner wants to move out, or one co-owner wants to move in.. and many other possible scenarios, etc.
If it is a BFA, please let me know, and we can discuss further...
Kind regards,