I'm an accountant by trade.

The designer talked about has a completely different account then the designers I usually recommend, and I would have had red flags to begin with.

When you pay cash for a $400,000 home and rent it out, your rate of return will likely be less than 6%.You could invest in stocks and earn 7% or better.You could put the money in a high-interest savings account and earn up to 5%.I don't understand why anyone would pay cash for real estate, erasing many benefits that increase the rate of return, while exposing themselves to the risk of loss (turnover costs, bad tenants, capex, etc.). 

I’d hold the PM accountable for poor oversight—they should’ve been more proactive.That said, it’s also important to weigh the long-term relationship with your PM.

Rather than use credit score as a criteria, I reject for consumer accounts in collections and unpaid civil judgments.

Don to me  passive you are not on the Checking account and Active you are on the checking account.

However, I've learned a lot from that experience and am willing start over again- Make sure you stay on the top of them and fully account for the draws being taken as if they (Builder) have multiple projects I've seen where one individual's draw gets comingled with another property.

@Megan HerringtonBigger Pockets is a great place to find a real estate tax accountant. 

Here are a couple of ways you could structure the deal:Lease Option with Seller Financing: You could lease the property with an option to buy later, allowing you to rehab it while giving the sellers time to find a 1031 replacement property.Seller Financing with Deferred Payment: Structure the seller financing with no immediate payments, allowing you to refinance once the property is appraised, and the sellers can complete the 1031 exchange when ready.Escrow Holdback: Transfer the deed into an escrow account, giving you control without immediate transfer, so the sellers can take their time with the 1031.Third-Party Facilitation: Use a qualified intermediary to hold funds and facilitate the 1031 exchange while you refinance.These options allow flexibility for both you and the sellers.

It may be that they are underwriting the property at a significantly different valuation than what you are using or that they feel that you or the deal is excessively risky.Great advice here, and a good HML will have an account rep or someone to communicate with you through the process so that you know.