Aside from the legal aspects, primarily they will address your personal needs and future plans as well as your partner's.What I have learned from past partnerships, be sure to address exit plans and what happens should a partner become unable or unwilling to contribute to the partnership or dies.

Long term owner financing would allow for lease optioning or long term leasing but seller is unwilling so those are out.

You say:due to the neighborhood and slower sales market here they were forced to rent it outWhen I see statements like this, I hear "they were unwilling to eat the loss at the time, so they rented hoping for better prices in the future.

After making mistakes, remembering the hassles I encountered due to some of my decisions, I was better able to draw upon experiences and relate them to callers and weave these stories into the way I communicate with would-be sellers who are/were astonished that I was unwilling to fall all over myself to pay what they wanted for their home. 

I am unwilling to pay this bill after I paid almost $300 to have it done last year.Advice?

I also base pay off percentage of work complete for each line item. you both must agree to the percentage at time of pay. up front on the contract I state that I hold a 10% retainage from all billings to be paid upon final satisfactory completion. regardless of the area you are in ( the company i work for, i bid work in every state) it is acceptable for  you to utilize the basics of contracting including detailing out a scope of work, paying based on percentages of individual milestones, holding retainage to ensure satasfactory completion. now some small time contractors may be unwilling to work with you because its obvious the standard you will hold them to and they wont be as easily able to half *** their way through the work and blame you for not being specific. but most will, and may even prefer it as long as this is discussed and detailed in the executed contract.

In my few phone conversations with them, they seem unwilling to negotiate and don't care that I am buying 3 lots for cash, so we will see how it goes.

Or the $250 plumber for the caulk leak or the $105 to instal and $125 microwave because the tenant was unwilling. 

The wife was on board to counter but her husband is unwilling believing that if they weight until the spring they can get more money.

People usually want both, and contractors unwilling to compete on price as well as quality are sometimes astonished and indignant to find themselves out of work in tight markets.