Once you're past your 20's it's next to impossible to have a signficant change in career without some sort of previous experience and this doesn't just apply to plumbing. If you're in the construction industry already you'll find it easier than someone coming from the service sector, for example.
Only real way to get going is to become self employed but that can be very risky and a hard slog. The cost of the course will pale into insignificance when compared to buying a van, tools, another course or two (say gas, oil, unvented or whatever), insurance and so on. Then your first jobs will be changing washers, fixing wc's and one off half hour jobs. Then you have to learn how to run a business, how to survive on no earnings for many months, etc.
On the positive side I trained at RF and thought their training was brilliant. Beware the sales chat though as it only applies to the successful people. On my course I'm the only one of the eight who made it into a decent wage - all the others returned to previous jobs. If you do go, say "Hi" to Danny for me (he called me the plum plumber).