The amount of money you have available for down payment impacts on all aspects of buying a home, namely how you write your purchase offer and the home loan programs you qualify for. A home loan calculator is a very useful tool which tells you what you can afford, which you need to know before you start to look for your dream home.
With the home loan calculators, you will be able to know if you will have enough available for a minimum down payment. This is important because some home loan programs are limited to only a few types of mortgages. If you have enough for a down payment, but need the lender or seller to cover all or part of your closing costs, this further limit your options and it is important for you to know this in advance before you start talking to the homes sellers or realtors.
If you intend to borrow all or a part of the down payment from your 401K or retirement plan, different loan programs have different rules on how you qualify. If a potential borrower has enough money for a large down payment, then they have a lot of options.