Very little long term rental of extinguishers occurs these days as most enlightened users have worked out that it is a con, for which they could afford to buy a new extinguisher every year instead.
Most rental is short term, particularly at events (and some of the utter junk some extinguisher companies rent out from their condemned piles astounds me!) and is an add on service, not the bread and butter.
There is a lot to being competent in the extinguisher trade (which sadly to few people are these days) it's not just having set off a few and then done the (increasingly short) trade body courses which actually aren't themselves complete and misses out several important things (I've had people who have done these recently that I've had to teach how to recharge stored pressure extinguishers step by step as they didn't go anywhere near an N2 cylinder, adapters, etc on their course, not even on paper!)
Then there is the investment in the correct tools, testing equipment and full set of spares to do the job properly.
A large number of people who set up the better independent firms have done their time (& training and experience) with a large national first and that's the best way to enter the industry unless you want to be a rag & tagger (the lowest of the low).
Fire Alarms are another area where you can easily mess up with a little knowledge as sparkies keep finding out.
If you have no fire safety experience then you shouldn't even be contemplating Fire Risk Assessments without a lot of training & on the job experience. We have trained assessors from scratch who only had a H&S background, but it's a process of years with courses, tutored FRA visits, audit and mentoring that still continues long after they are allowed to do FRA's themselves (starting with revisits and low risk small sites).
My advice is to be an apprentice/trainee with an established firm and after a few years if you feel appropriate start up yourself.
I am willing to advise you on the extinguisher front if you are gong to do it properly, but if you end up being a rag and tagger hope I do ot come across your work as I 'out' to clients any firm who is obviously not doing the job right.
First free tip - don't put a foam, CO2 or ABC Powder extinguisher in a commercial kitchen with cooking oil fryers over 3 litres/300mm diameter as sole protection even with a fire blanket - it requires Wet Chemical (so many smaller firms do this because of ignorance or just to get a sale)
