Let to buy if moving abroad?

I own my house outright having bought it from an inheritance. It is in a small northern town and only worth c. £100-110,000 but I have no mortgage, and indeed wouldn’t be eligible to get one due to irregular income.

I am considering a move overseas (to a country I have lived in before) and my next-door neighbours, who rent privately, and whom I’m quite good friends with, have expressed an interest in renting my house from me, as they have long been unhappy with their current landlord.

I had assumed that if I moved abroad I would sell my property in order to raise money for the move, for my child’s education abroad, and for other related expenses (I would be renting in my new location, no matter what, as buying property there is prohibitively expensive and difficult for foreigners anyway). I have no particular plan to return to the UK in the foreseeable future so this wasn’t much of an issue for me. However the prospect of being able to keep my property on and derive some income from it is tempting, and I would have the peace of mind of having tenants I know and trust. Also the guy is a builder so he would be able to maintain the property for me.

However, I still need to raise a large cash sum. I have heard of ‘Let to buy’ mortgages where a mortgage can be taken out on an existing property if the owner plans to vacate it and let it out while living elsewhere. Given that I would have a tenant ready to move in, would I be able to get such a mortgage in this case? Could I use the projected rent payments (which I could get legally agreed in advance) as my income in terms of affordability criteria? Would any of this be affected if I wanted to give my tenant a ‘payment holiday’ in return for house repairs (eg. the first three months rent-free if he fitted a new bathroom, etc)?

Thanks in advance.