Simpson is a company that supplies the connectors for structural work, so maybe the contractor is quoting you the retrofit using their products? 

Sure a PA can require a Seller to notify/supply the Buyer with copies of city notices, etc.

Seller financing was accepted with 19% downpayment, 20 year amortization, 15 year balloon and 18 months interest only payments.Majority of downpayment was funded through a family loan with similar terms to Seller financing.

I got some answers for you,#1 just buy the materials yourself, meet and maintain relationships with salesmans at supply houses.

Operating account for administrative stuff like signs or supplies. 

https://www.har.com/content/newsroom/Houston Real Estate Highlights in April: Single-family home sales rose 7.8 percent year-over-year, with 7,586 units sold, marking the third consecutive month of positive sales and the biggest volume increase of 2019;On a year-to-date basis, single-family home sales are 2.2 percent ahead of 2018’s record pace;Days on Market (DOM) for single-family homes edged up from 56 to 57 days;Total property sales increased 7.8 percent, with 9,063 units sold;Total dollar volume jumped 9.6 percent to about $2.7 billion;The single-family home median price rose 2.1 percent to $245,000, achieving an April high;The single-family home average price was up 1.9 percent to an April high of $310,676 – the second highest average of all time;Single-family homes months of inventory reached a 4.0-months supply, up from 3.5 months last April and the most plentiful level since September 2018.

Are rentals in short supply there or are there plenty of units available?

Worst case if something happens to the developer, you would have the land.Reality is at this time supply and demand are in favor of sellers (developers).

The growth in the Daytona Area and the limited supply of rentals has really pushed rents up. 

Find an owner who'd owner finance a large % and I'd borrow a small down payment from family, have an amortization schedule that allows cash flow with a several year balloon payment, and refinance in several years to pull out equity to buy another property and pay off the owner. 2.