Good afternoon, Judith! First off, I fully agree with everyone who suggested that you hire a Realtor or a real etstate attorney. As Amit noted, a professional Realtor does not cost you anything yet you will have benefit of their experience and advice.
Second, I agree again with Amit when he advised you to contact Coldwell Banker Home Loans. CBHL does not charge lender fees which will save you quite a bit of money in your total closing costs. They also have hundreds of loan programs to choose from and excellent guarantees to you as the borrower.
Now my question to you: When you indicate that they want a $5000 'deposit', have you clarified with them whether this is your 'downpayment' or actually the 'deposit'? These refer to entirely different things. Your downpayment is who much of your own cash you are putting towards the purchase (not including costs to close). $5000 is approximately 3% of the $157,000 purchase price you mentioned, and this would be about the smallest downpayment possible in today's market.
Your 'deposit', on the other hand, is the amount you put into escrow at the start of the transaction to ensure that you will complete the purchase. As others have noted, the higher the deposit, the more secure the Seller will be about your offer, but unless the Seller has already made it a requirement of sale, it does not have to be $5000. Moreover, your deposit is not in addition to your downpayment and closing costs. It is simply a part of the amount of cash you will need to complete the transaction anyway.
Again, I strongly recommend that you sit down with a Realtor or a real estate attorney who can go over the documents you have. We can explain and advise you as to each item that is causing you concern. If I can help further, please do not hesitate to call me at 305-801-3133