Is it true my paycheck will get bigger when I buy a home?
Yes, if you're renting now or if your mortgage interest payments are higher than you pay now. Buying a home adds to your "take home" paycheck because you can increase your withholding allowances in anticipation of mortgage interest payment deductions on you next tax return. By increasing your allowances, you reduce the amount withheld to pay future taxes --- which puts your tax refund in your paycheck today, not at the end of the year.
Ask your tax preparer to estimate how many allowances you should claim to compensate for reduced taxes caused by the interest deductions.