I live in an apartment complex and saw a guy in the concierge earlier - he checked me out and I found him cute but didn't think much more of it. He went out of the building and then came back and I overheard him telling the receptionist his flat number which happens to be in the same building as me. I left the concierge, went back to my flat, and then he was walking in to my apartment building as I was leaving it a few minutes later. I held the door out for him as he had lots of stuff, he thanked me and I said it was OK. I think he is so cute and I want to know him but I don't want to come off as desperate. Right now I know nothing about him, just his flat number. I don't know if he is single but I kinda got the feeling he found me attractive. I was in my gym gear which I guess helps, and I was standing next to him at one point and it was a little awkward for both of us which I don't think it would have been if he found me ugly. I'm usually quite good at judging whether someone is in to me but for all I know he could be living with a girlfriend. I know there's a chance I may bump in to him again, but there are usually so many people around the complex that I may even struggle to pick him out/ have forgotten what he looks like. I would like to get my message across effectively but I don't want to have my pride hurt, say if he is taken or is not interested. I also don't want to come off as easy. I was thinking of slipping a note in his letterbox/under his door to ask him out. This could go one way or the other though and if he declines/doesn't respond at all I'm not sure I could face the embarrassment of potentially seeing him around.Would you find it weird if you received such a note?