The monthly payment on a three-hundred-thousand-dollar mortgage amortized over 30 years depends entirely on the prevailing interest rate secured by the homebuyer. Assuming a representative market interest rate of 6.5 percent, the monthly principal and interest payment comes out to approximately $1,896.20. If interest rates rise to 7.5 percent, the monthly requirement increases to roughly $2,097.64. In addition to these core principal and interest figures, homeowners must budget for mandatory monthly escrow expenses covering local property taxes, hazard insurance, and potentially private mortgage insurance if the initial down payment was less than 20 percent of the purchase price.