If there's no way you can afford it (that sucks. But maybe asking about cleaning mats will work), look at any boxing, muay thai, bjj or even judo around if it's cheaper. It'll give you some transferable skills, like physical skills but also training (like how you should approach and learn from sessions) and maybe competition experience. Or just go to the MMA gym less often if that's an option, since it's better than just not going.
You can drill a couple things at home (better to practice just a few things and do them correctly. Like when I first wanted to train and couldn't go to a gym I just found out the correct way to jab, pravticed it slowly, learnt to get it quicker and did at least 100 or so daily for a few months, then similarly drilled the straight and 1-2 next to a wall to keep it straight. When I trained with others nobody could tell I was self-taught. Then you wanna add in the small head movements so your head isn't in the centre to be countered plus think about where your non-punching hand is and how you exit from punching, but you'll have to do your own research).
If you can even go to a couple of boxing classes that'd give you a tiny bit of experience so you can have a couple pointers and visualise better at home. Maybe you can go to like one class a week in the MMA gym (you probably would be better off only going a few times a week at first even if you had full membership, while your body adjusts) and that'll give you stuff to practice at home. Or if not, some bodybuilding gyms might have a ring and someone who hires it to do small classes which cost more per session but you'll get a little more attention. There was a top boxer from cuba (kid chocolate) and a top muay thai pro in thailand (Yodkhunpon Sittraiphum) who apparently learnt a lot early in their career from watching others and shadowboxing.
And focus on getting in/keeping in good shape and getting those habits of regularly exercising or jogging (a lot of pro fighters run like 10k daily, but obv you build to that), how to cook/eat or whatever you need to work on. Nothing crazy. That way when you can afford to train, your conditioning will be closer to where it needs to be to make the most of sessions.
Easy to overdo it training at home, when you're highly motivated. Slow, steady and injury free wins. And definitely no point getting hurt while doing sub-optimal training. GL.