@Cirilo Villar You could do a contract for deed where the seller still holds title until all conditions are met no due on sale or Take the first subject 2 and seller carries a second or the seller does a wrap for the amount he wants to finance.
Land contracts also depends on the state as some states do not allow any mortgage on the property and some will state the mortgage cannot be greater than the land contract value.
If there is a mortgage on the property it makes it very difficult and risky. What if the seller takes your $ and payments and doesn’t pay the mortgage? The bank is in first position so they will foreclose...