So you already have competition so its not exactly a niche market.

I'm sure you could suppliment your income if you wanted but you need to be different. I would think of different pieces of equipment that the normal gym doesn't have to attract people in like tyres, chains, yokes, sleds, box jumping etc etc.

There seems to be a trend at the moment for back to basics training outside. I am seeing lots of normal people joining up to these bootcamps in the morning. Employ someone to run this style event.. The money isn't going to come from your meatheads that pay £20 a month, its going to be from the fad trainers.

Also advise on nutrition too, keto diets seem to be the trend. You might need to go back to school to get some qualifications.

You need to do a bit extra imo like putting on some events to draw people in. Charity type things or seminars with bodybuilders, local powerlifting/strength comp, get members to form a tug of war team. ind you, thats a long way off.

If your serious with it then good luck.