We've just sold our UK house, but rented it out for the last 6 years.
We vetted all the applicants and ended up renting to friends of friends of friends. They moved out but recommended another family to move in, so we had a Skype with them and they seemed good + paid 6 months rent upfront. Honestly, both sets of tenants treated the house better than we did, so they were easy from that perspective.
In terms of maintenance we had trusted friends who are tradesmen who could do the jobs that needed doing (eg electrician, plumber, builders), and DH took care of coordinating that with them and the tenants as needed. So we negotiated a fee of 4% with our agents because they were essentially just collecting rent / advising on contracts etc - everything else was with us.
Totally agree to look into the financial side of it - ie the mortgage and taxes.
Our original mortgage provider granted permission for us to rent it out for 1 year, then extended for another year, but after that refused and said we needed to revert to the default/standard rate (or whatever it was called) as they couldn't offer us other products as non-residents. In the end we moved to HSBC expat who were pretty much the only other company who would touch us. It might've changed now, but at the time they insisted on opening a current account with them too and maintaining a balance of min GBP 60k. We managed to negotiate a small monthly fee in lieu of the 60k balance. But if I recall it was a right pain to open and took a few months.
We were classed as non-resident landlords so yes still had to do a UK tax return and also declare the UK rental income in our tax return here. But that was all quite straightforward and we always managed to remain just below the personal allowance each.
Selling was quite straightforward too actually... no CGT where we live, though obvs have the UK side to contend with for our 2023/24 tax return.
So all in all it was pretty easy really. A few hurdles, but I am used to admin and challenges so none of it bothered me, though DH was stressed at times god knows why as I was the one doing it all!!