I don´t advise trying to sneak people into a room.
1st-It seems near impossible to do on with the layout of the lobby´s I´ve seen.
2nd- If you can´t afford a room, you probably aren´t going to be able to afford a lot of stuff (food, travel, etc.)
3rd- What happens when you get caught and kicked out with no money?
Its not a bad question to ask, but there is a difference between traveling cheap and being cheap. Good luck.