This is only true insofar in that if a guy is using you for sex, that will generally become apparent after you have sex with them. So your key takeaway here is not that he's weird, but that he didn't immediately offer you cab fare and was trying to be nice.
If you want a sense of where your overall relationship is heading, then you need to talk to him about it. Ask him how he sees things? Friends with benefits? Heading towards exclusive? That'll tell you a lot more than trying to read into a bodega run.