This is actually a notoriously common scam amongst bums. We got a lot of them in my area, so I'm used to this happening, allow me to explain...
You see, spring time is mating season for bums, except they don't mate like typical mammals...
The "beans" that bum gave you were not in fact beans, but larvae. You see, bums are capable of reproducing by themselves, but can't nurture their young, so they'll often give them away in their pre-developed stages as "magical beans" due to their resemblance to such. The only thing that's going to happen once the larvae, or "beans", develop is that the infant bums will mature and you'll begin to notice a lack of food and silverware around your house. The best course of action would be to burn them, OP. They tend to stick around as they get older, you don't want that.