Re: Is it worth it?
Yes and no.
There are some great refrigeration jobs out there and the diyer is less likely to get involved himself. Some of the “American” jobs are well worth taking as you can charge a lot more to do them and a lot are simple faults, would give the Samsungs a miss though!
There is however an awful lot of BER jobs out there and seemingly endless frost free defrosting problems that you can never be 100{e5d1b7155a01ef1f3b9c9968eaba33524ee81600d00d4be2b4d93ac2e58cec2d} certain you have fixed-or can even be fixed. These will depress you to the point of giving up altogether.
By “trained up” I guess you mean system work, this has dropped away a lot in the past couple of years. Re-couping your outlay on training and equipment will not be easy.