As I understand it, if you are self-employed, you would need to pay around 250€ a month just in Social Security. As Muppet says, that really is a lot of key rings.
These are issued (or not) by the town halls.
Do a business plan. Pretend you are going to operate this business in say Brighton or Blackpool. And go to the bank and try and get a loan for say £10k. I know you might not need the money but having them pick over your plan will give you a good insight into how watertight it is.
Maybe forget all the rules and just give it a go for a couple of weeks and see how you go before you invest in becoming official.
There are quite a few that do this kind of thing as a part time enterprise, no paperwork etc.
Even they cannot make a living out of it without another job
POSTS ON TENERIFE FORUM ARE NOT ACTIVELY MONITORED