I'm sorry you're having not-peeing-in-the-box issues.
I can't say for sure, of course, but peeing out of the box was always an indication of a UTI with my kitty. The fact that your kitty is trying to use his box also suggests to me (though I'm not an expert) that this might be medical rather than behavioral. UTIs are often painful, so kitties associate the pain with the litterbox and avoid it. Kitties don't generally start avoiding the box for no reason.
Is he not always producing urine when he goes into his box? If he's at least peeing, that's a good thing.
It might not be a UTI but some other type of issue with the urinary tract. But a UTI would require antibiotics. The vet would probably want a urinalysis, which is an added cost, though not ferociously expensive (my vet charges $40). But you could call your vet, tell them that money is an issue, and see what they're willing to do. Who knows, maybe they'd prescribe an antibiotic without an exam or urinalysis. If not, I think you'll have to find a way to make the finances work, because if a UTI isn't treated, it can lead to stones, or worse, a blocked urethra, which can be fatal. Maybe you can postpone payment, or work out a payment plan, or apply to other sources that might provide financial assistance? There may be a list posted in the stickies in the health & nutrition forum.
Please do monitor your kitty's peeing. If hasn't peed after about 12-18 hours, I would worry. Without any exaggeration, it becomes life-threatening after 24 hours, because toxins normally flushed out in urine instead build up in the body.
Bitter orange spray, you mean to deter peeing in other spots? He'll just find new places if it's a medical issue. But do make sure to use an enzymatic cleaner specifically formulated to break down kitty pee for areas where he's already peed. Other cleaners will get rid of the smell for you, but not for your kitty, so he'll tend to go back to those same places.
I wish I could offer you options that don't cost money, but in this case, I'm not sure that's possible, but maybe others will have other ideas for you.