What are the legalities if I were to rent out a room short term, just to people on vacation for a week or so here and there (maybe a total of 1 or 2 weeks per month). No food included. Besides submitting the income from this on my tax returns, would I need to do anything else? I'm thinking of doing this to help out with my mortgage.

You need to check zoning laws as this might run afoul of them.

Your home would need to be zoned either multi family or for a rooming house. ( or for a bed and breakfeast, what ever type of zonning rules your local government has) Your city may also require a business license.

The thing is that I live in the house and will be living there. Its just a way to get a little extra income. I would be doing it maybe only once or twice a month for maybe a few days at a time. It wouldn't be a bed and breakfast. Room only for out of town guests... who would pay me a small amount.