Plus it isn't limited to specific algorithms for mining so you can mine a bit of everything.
That is right. You can also sell it if you do not want to mine. The ASIC will have no resale value after a year.
For the ASIC such as S3 and S5, if you do not have free electricity, they are not profitalbe to mine at the moment.
That could be said for s7 too. With 0.06 $ per kW electricity cost (which is considered medium to low) S7 makes about 40$ per month profit, and they are still being sold for 400-500$. Can't even image what would case be with s3 and s5 (less than 5-10$ per month or smth like that...)
@OP That tells you that investing in asics is not so good idea if you want only few of them.