I decided to rent my place out that I was living in to someone in October, 2006. When I calculate the Mortgage Interest for the rental do I just calculate the interest paid during October through December of 2006 since those are the months I rented the property out?

I know these things are complicated and there are several different types of mortages and considerations. I've never bought property before and hope to buy my first place in 12 months. In order to do some basic research, how can I calculate what a mortgage might be? A friend told me something like for every $100k in the loan, you can expect your mortgage to be $xxx. I forget what xxx equals.

I keep thinking I am doing it wrong. I use to work as a loan processer, but all I had to do was enter the figures into CAYLX software and it did the math for me. So just to assure I am not screwing up... Can someone tell me how to come up with the monthly mortgage payments? I want to be able to figure it out on my own!

Experts say that a person's mortgage payment should be no more than 30% of their monthly income. Is this 30% of net income or 30% of gross income? Do they consider the mortgage payment to be P&I only or should property taxes also be included in the 30%?