I just established a new relationship with a real estate agent and the first thing I received in my inbox was a buyer agreement.

Sure you want the property to perform but I also filled out a PFS (personal financial statement) and had to supply all of the supporting documentation. 

You'll get more accurate advice and answers, and they will probably be more willing to work with you and guide you in the right direction if they have documentation to look at (tax returns, W2s, amounts you paid for each property, taxes, insurance costs, estimated rents and completed values, etc).

In fact, I received better brochures from some of the other companies I interviewed (however, these companies had fatal flaws noted above). 

You may also want to hire a lawyer to review the title documents to see if he or she can help you sort the mess.But I would again stress that the quality of a settlement agent varies greatly.

Any other documents that I need?

Although we are contributing 60% of the equity, the experienced developer we are most interested In partnering with is proposing we receive only 18% of the cash flow once the property is built and stabilized.

If your asking these questions here, find a friend who can help so you don't get fleeced.Drawback is usually the loan is more expensive/higher rate, they may not report to credit agencies (won't improve your credit, but this can keep your documented DTI ratio lower which may be good) and if they do use a servicer, somebody (you, unless you negotiate otherwise) will pay a service fee to have your money processed every month.

If you start to make contributions along with receiving a company match - you will notice the amount adds up and a 401K loan can help you with your first rental purchase.and Welcome to Biggerpockets!

I checked and I did not receive any notice about the increase in price.