We have one BTL that was sort of accidental, largely down to a dd's mortgage (we were going halves with her) being turned down at the last minute because of an absentee freeholder. Having intended to live in it she then took fright at all the complications, and we went ahead anyway.
It has worked out well for us - we've been lucky in having had a very good lead tenant since the beginning, but then we always see very promptly to any repairs - or get the managing agent to do so - and have not been greedy with the rent - in fact we have never raised it. I am all too aware that we've been lucky, though. If the current tenants decided to leave, I think we would probably sell.
However we bought in 2010, since when prices (around here anyway) have soared into the realms of the ridiculous, though they are beginning to come down now. Given yields at current prices I doubt I'd embark on it now.
It does depend so much on prices/rents/demand where you are living or thinking of, and of course you have to take into account recent tax changes, which could seriously affect any income.
You absolutely must do your own very thorough research, and not be guided by what any estate agent or other property-investment advisor may tell you. (Though I am sure you would do this anyway.)
I have heard of too many cases of BTL investors coming very badly unstuck, having bought in areas they don't know at all, and having done no research of their own - after being sold the property by some very persuasive property investment 'expert' (aka shark) or other.