Mortgage math is the start, not the decision
Principal and interest follow a standard amortization formula — fixed rate, fixed term, predictable payment. Escrow for taxes and insurance sits on top and changes with locality and carrier.
Extra principal payments shorten the loan and reduce total interest, but liquidity matters. Cash in the home is harder to access than cash in the bank unless you refinance or sell.
Use this for screening. Lenders also weigh credit, DTI, reserves, and closing costs. Pair with the DTI calculator before you apply.