I’ve been thinking about this OP.
Ten years ago when he was 24 he was given / inherited some money from his parents when they sold their family business. He and his sibling used this cash as a deposit to buy some BTL ? residential properties. ( I’m a bit confused why the OP would have been in them if they tenanted ).
My guess is that the fiancé then spent ( his share of ) the rental income rather than using it to pay the costs - mortgage, insurance , letting agent, tax.
I’m also guessing that rather than him regarding this as extra money each month on top if his wages, that he quit his job or Never got one and though he could live off the income . You need A LOT of capital and properties to be able to do this. And be smart ( which I strongly suspect he’s not ).
So maybe that why he had to borrow money to pay these basic costs. And that his “ investments “ are these debts or gambling debts. Or he might have invested in risky schemes which have come to nothing.
Either way, he’s not been very smart with money. Though clearly his sibling IS a lot smarter, if they have refused to allow him to borrow against the property .
Which is why he’s asking the OP to take out an unsecured loan in her name.
Either that or he’s maxed out his credit cards already.
Like PP I don’t think it’s anything to do with an interest rate increase on an existing loan. I think it’s that he CANT borrow anymore on his existing
Properties.
Another possibility is that his recent “ crisis “ might be related to the tax changes for landlords that come in this week with the new tax year.
If he bought his properties 10 years ago, he would have been able to deduct all of this interest on his mortgage from his rental income before tax was paid. But now there’s no tax relief cor capital repayments of mortgages, he will just gets a 20% tax credit instead. This change has been phased in over 5 years, it’s not like it’s a surprise.
I might be wrong and this is nothing to do with it. It might just be that he’s no longer able to service his debt from his rental ( or other ) income.
If they are not repairing and renovating the properties, their rental income might have dropped or perhaps there’s been vacancies or their costs have gone up in another way.
One way this guy IS smart is that he’s moved in with a woman who is good with money and is getting her to subsidise his living costs.
Op have you thought of checking your own credit history to see if he’s taken out any loans in your name already ?