Generally speaking if a rapid test is negative, you don't have enough viral load to be contagious. My son only tested postive for 4 days, with symptoms (maybe actually only three, because I didn't have him test on day 4). The first day he had a headache and slight fever. By day three (still positive on a rapid) he was riding his bike in the driveway and playing with his lacrosse rebounder. Oodle of energy. On day 5 he tested negative and I let him resume normal life.
If you tested negative two days in a row, I'd say you are in the clear.
A friend of ours tested positive the other day with zero symptoms. He had visited his daughter away at college for 24 hours; while he was there, she tested positive (she had a previous possible exposure, so her being positive wasn't really a surprise), and then he tested positive the next day when he returned home. It's highly unlikely he got it from her AND tested positive within 24 hours or less....even the newest strains have a 2-3 day incubation period. I strongly believe he caught it sometime before his visit and was asymptomatic and it was coincidental that he tested positive when getting home....but of course we will never really know for sure.