I have sunbeds and my advice is this...
Sunbed users know a good sunbed when they find one. If your bed isn't good, it won't get used. You should find out if there are other salons with sunbeds near to you and if so, you'll need to make sure your bed is as good as or better than theirs.
They're expensive and use tons of electricity so don't invest unless you're sure it'll be used.
Oh and... before getting a sunbed, you should check if it needs to run on 3 phase electricity. If it does and you don't have it, it costs around £3000 or so to convert from single phase (you can get beds that run on single phase).
On a brighter note... my beds have been pretty much non-stop since just after lunchtime today. There are a lot of people wanting to use sunbeds even when the sun is shining.