What you need down and what your monthly payments are depends on your individual financial situation, credit score and what kind of loan program you can qualify for. If you only qualify for a loan that requires 20% down, ..well, ..you need 20% down and from that .. you look at what price point of house you're buying ...which you can then figure out what your monthly payments are. There isn't a set downpayment or monthly payment for a particular house ... so no point in asking for every single house you're interested...it is all dependent on your financial situation. Talk to a bank/lender to see what kind of loan program would best suit your needs and qualifications.
It's not like a rental property where you have a set amount to move in ..like first and last + deposit and it changes for each house.