How much can you afford?
The best way to determine this is to seek out a lender and have them give you an analisis of your current finacial position. They will ultimatly give you a preapproval letter. This will let you know how much house you can afford. I have several resources that can help with this,just ask.
When should I start looking ?
Start looking right away. The longer you look the better you will be at determining what is available and be able to compare properties against each other for condition, price and size.