Quote from @Micheal Smoke: Hi, my name is Mike Smoke, and I'm an aspiring real estate investor focusing on multifamily and Section 8 properties in the U.S. as the barrier to entry is much much lower in terms of price compared to Canada and Funding options. 

Talk to the seller, but options are to cancel the sale (and risk losing your deposit), renegotiate to lower the price to allow you to fix the problems or ask them to fix it. 

With the duplex, you can do both rental options.  

If you're considering purchasing under a business name, consult a CPA or attorney for setup and financing options.

These are very different than Subject-To, as the loan actually transfers to your son's name, and off the seller's name. 

I'm open to helping you explore your options.

If you ever need guidance on financing options for flips, rentals, or new construction, I’d be happy to help.

If everything checks out, they could be a solid option for your first investment deal.

I know there are a lot of options, especially since they are family and willing to carry the loan. 

The reason why I ask is because that could determine what loan options are available to you (and interest rates).