The real answer depends on what role you land - a lead will destroy your schedule, but ensemble or smaller parts are genuinely manageable alongside full-time work. I auditioned for a local production last year mostly to get out of the house and try something new, and got cast in a supporting role. Rehearsals were maybe three nights a week for two months leading up to opening, then scaled back to twice a week for the final month. That's totally doable if you're willing to skip some Netflix time and plan your evenings around it.
The financial side is honestly the least of your worries. Yeah, you'll spend maybe $30-50 on costume pieces they won't provide, possibly throw in $10-20 for set materials if the theater asks, and some groups charge modest membership fees (maybe $25 annually?). What you won't get is paid - this is pure hobby territory. But the thing most people don't mention is how much the experience itself is worth. You meet people outside your normal circle, learn some actual skills, and there's something satisfying about being part of something collaborative that isn't work-related.
The bigger question is whether you genuinely want to do this or if you're looking for a side income stream. If it's the latter, community theater isn't it. If you just want an outlet that gets you on stage without needing to be a professional, it's absolutely worth auditioning. Start with one production and see how the time commitment actually feels for you - everyone's circumstances are different, and what worked in my schedule might be tight in yours.