Stupid and irresponsible. It screws up the market for the majority who can't afford it and makes companys think they can get away with making us pay for everything. We already have shysters out there making applicants pay for submitting a cv, interviews and sim rides. We'll all be paying for recurrent sims next.
So you shell out £15K for a 737 rating and get offered a job on an airbus. Own goal! Or you do get a 737 job, but the employer quite reasonably insists you have to do their course as you have no hours, result, bonded for 3 yrs anyway. (I've seen it)
DO NOT DO IT