For normal home purchases, in order to buy a house for $100,000, you will have to come up with $20,000 as a down payment if you have conventional financing (no FHA insurance or VA guarantee) and no private mortgage insurance (PMI). That is because of requirements made by the investors who buy home mortgages after they are originated.
Commercial loans are entirely different. Borrowers with good credit and good reputations in the community can borrow 100% or more of the purchase price for rental houses, so long as the debt service coverage ratio (DSCR) is 1.2 or better, in other words, if your annual cash flow is 20% more than your annual mortgage payments. Lenders like to know that your property income is enough to make the mortgage payments, even if you have some unusual expenses or greater than ordinary vacancies.
The other way to obtain 100% financing, and sometimes even more, is to have a believable plan to rehab or repair the property and increase its value. This depends on giving your lender a detailed budget for rehab and repair expenses, a timeline for completing them and selling the house or obtaining permanent financing, and the estimated value of the home after the repairs.
You must support your estimated value by providing an appraisal, or by supplying your lender with information about recent sales of properties comparable to your own, after the house is completed.