It would adjust your AGI down. So if you have 40k taxable income and you have 6k in mortgage interest and property taxes, you would owe tax on 34k, not 40k. Also, it only works if the amount is more than the automatic standard deduction
Never dealt with it, will let someone else answer
Seller basically pays your realtor. In reality, the commission is split between the selling agent and buying agent. You pay nothing.
Well my place is 1500 sq ft, keep furnace on 74 and ac on 70, gas,water, sewer, electric is about $275/month
Closing costs don't really change that much on the amount of the home. Expect 2-5k. 1 year of homeowners insurance has to be paid up front, but you get a credit for taxes. Try to negotiate seller paid closing costs. Helps out a lot.