Network with reputable private money lenders by attending local real estate meetings or joining online forums.

Make sure to check reviews and go with a reputable one!

If my contractor has a favorite supplier or know where to get good prices I am happy to go with that.

Hopefully someone from the area can chime in but shopping quotes from reputable and well rated or referred PMs will illustrate a better picture for you.

If you haven't already - find a reputable lender to qualify you and give you idea of what your PITI would be at 600K or other price point. 

However, you can expect to recover about 50-55% of your investment when selling the home.Another good option would be to consider converting attic space, finishing a basement, or repurposing a large living area to add a bedroom without expanding the home's footprint.Some other tips to help you save on materials while still creating an appealing finished product: buy in bulk, shop at discount stores and outlets, look for overstock, discontinued items, or slightly imperfect materials, attend auctions and Estate sales, incorporate reclaimed wood, vintage fixtures, or other salvaged items for a unique look at a lower cost, build relationships with suppliers...If you have any more questions or are looking for funding please feel free to reach out to us, we're a private lender.Regards,Jackson

So here is my question, I know a reputable firm that provides this service but how can I set up the 'business partnership' where they are my chosen vendor for this service without my clients trying to go behind my back to deal with them directly, thereby kicking me out the middle.

However there are some reputable new construction builders in the area.There is, as you likely know, a housing shortage and, once Caesars Casino opens at the end of 2024, they anticipate 2 million visitors a year. 

The costs of a QI are also often relatively minimal in comparison to the interest and penalties you would pay if it is blown up.You are also parking significant sums of money with the QI - that alone is worth using a reputable QI to ensure your funds don't disappear. 

Having lenders or partners upfront places you in a better and more confident negotiating position and in the event you find a deal and can't find the money, now you lost the deal and have to back out damaging your reputation as a closer.