for one it will not go through with out a down payment .
to hold the house you need earnest money . That is between 1000.00 on up . Usually just 1000.00 .
The mortgage company , and banks then see if you have the down payment in your bank , match your living costs to your pay , check to see your credit ratio ,
If you have 20% down payment on the house you are buying , that needs to be seen in your savings or checking acct .
example : a house that is 250,000 / down payment about 50,000. , This needs to be in there before you put a bid into that house.
Now you are going to be making payments on 200,000. loan.
you can put as much more money down , after you do the 20 % .
also note : do not go out and buy anything big, like a car while this is going on. Wait after ..