Senior cat won’t use litter box

My 15 year old male neutered cat won’t use the little box.

Not the best at cleaning the litter box. Been dealing with depression. I have now doing a lot more cleaning.

He’ll go potty anyway else including blankets, sheets, rugs, and clothes. He only goes if he’s forced to.

Can’t afford a vet. I’m afraid he might have arthritis or a UTI.

I’m worried he’s reaching the end of his life.