Should I pay off my mortgage or use the money for a deposit on a second property?

theguardian.com:

Q I’m a 42-year-old full-time professional and in a rather fortunate but tricky situation, which I would like your help with. My seven-year fixed-rate mortgage is coming to an end on 2 May 2023, after which I am not sure whether I should remortgage or pay off the balance.

I have about 20% of the mortgage left, which I could pay off as of today. However, I would incur an early repayment charge of just over £3,000, so I think I’d better wait until the fixed deal expires as the charge no longer applies once the mortgage is on a variable rate. If it’s paid off, I’d still have a bit of a safety net of about £10,000 left for any emergency expenses.

However, I am thinking of buying a new property in the near future and rent my current home out as it was always intended to be an investment, given its fantastic location near Elephant and Castle in London, just on the border of the tube zones 1 and 2, right in the middle of the regeneration area.

Should I pay off my remaining balance in May, be mortgage free then rent it out and start saving for a deposit for a second property or would I be better off using that large chunk of money towards the deposit for the second property and take a mortgage out on the 20% still remaining, hoping to get a favourable rate, given my large equity in the property already? KS

A I think it might be an idea to have a chat with your lender as even with fixed-rate mortgages you are usually allowed to overpay 10% of the outstanding loan each year without having to pay an early repayment charge (ERC). It would also be a good idea to ask your lender what its position would be if you decided to rent your property out. Would it give you “consent to let” without changing the terms of your mortgage (and for how