If they have an legally binding agreement, you need to honor that agreement and pay the fee.If you failed to mention to the agent that they are going to get paid, and then explained how, of course they won't present the offer.

We have modified many seller financed notes over the years (with input from the servicer and a qualified attorney as mentioned by others). 

In addition, when you have leverage you have the other benefits which @Ali Boone mention.

Here's a bit of visualization/data on some of the markets mentioned in this thread.

my condolences on your recent lost.there are a few ways you can do this, as mentioned above you can take a heloc on your primary residence which will give you a second mortgage, first mortgage payment wont be impacted. you can do cash out refinance which will give you one mortgage and payment. it will pay the old mortgage and give you money in your pocket to pay for the rehab.or you can do a renovation refinance which is similar to cash out refinance but we would contractor involved  as part of the refinancing and they are paid through the loan

If this is the case, would the original seller financing have to mention that the buyer (me) can re-sell the property at any time? 

Love Jim Rohn had not thought of him in a while thanks for mentioning him..

This is one of the things that @Matthew Irish-Jones mentioned above - be careful about putting #3 on his list above #1 and #2.

Also: I must have mentioned the request several times so it was clear.   

You also mentioned you started pretty young, I am 18 and just purchased my first college rental, any tips?