This question has been asked so many times on here that people mostly don't even bother replying now - sorry.
But here's a copy-and-paste from yours truly to a similar question recently:
"There will be a slew of people on here who will say you're mad to even think about it.
And they're right!
Lanzarote has picked up a bit in terms of numbers visiting, but the general pub and restaurant trade is still slow. People are going to the supermarket more than ever on their holidays.
There are a few places that are doing well, but most of them have a niche audience, be they customers of a certain age, return customers, betting/racing fans, and other unique selling points such as location, professional staff, popular musicians, quality food at reasonable prices, etc.
It sounds obvious, but few places can achieve all or even some of the above.
The good bars won't be for sale (or will be prohibitively expensive) and the other locales are empty for a reason.
Try and get a job in a bar on either island and stick at it for 12 months. Then you'll be in a better position to see what's what."buying-a-bar-at-the-min-good-or-bad-t7921.html