Mortgage or secured loan?

Sazzle1234

Hi all,
Im after some advice please.

My boyfriend owns his own leashold flat, an ex council property with over 100 years on the lease, he has no mortgage as he inherrited money and purchased the flat outright 10 years ago with that. He wants to do the flat up and consolidate some existing debts such as car finance and a boiler he purchased which has a long repayment plan attached. His credit file isn't good but this is due to one default from a company that went bust and he is currently in the process of getting it removed.
The plan is to do the flat up and sell it in a couple of years and take out a joint mortgage on another property.
He is looking for somewhere between 25000-30000 but doesn't have much money to pay upfront fees etc.
Should he be looking at a small mortgage or would a secured loan be more what he's after? What's the best option? Can you even take out a mortgage against a property when you own the property already? We're both quite new to this. He obviously won't have that amount of money paid off in a couple of years so something where we can use the sale of the flat to pay it off when we move would be the best bet.
Any advice would be very much appreciated.

Thanks