As a Realtor I am unable to determine the impact your credit score will have on your ability to get a loan. There are times when a sizable down payment could cancel out some of the effects of a low credit score, but credit score is one of many details lenders consider when deciding to approve a mortgage. They also consider your sources of verifiable income, job history, debts, and other assets. If you would like suggestions for lenders in our area, please call/email me and I'll be happy to provide their contact information.
Will the owner lower the price with a large down payment? That is also a hard question to answer. It can make a Seller feel more confident about an offer when they see a large down payment amount on the Buy-Sell Agreement. However, Sellers also look at other details such as contingencies, closing date, or other concessions requested by the Buyer. It also depends on how much you're asking them to take off the price -- are you talking 5% or 25%? Generally, unless the Seller is desperate for some reason or they realize their property was overpriced, they probably won't take 25% of the price, even for a cash offer. Most of the homes in our area are selling at between full price and 5% below full price. Every transaction has a life of its own since the people involved each have their own wants and needs. So if you are interested in a property you should make an offer -- you never know what's going to happen until you do.