After years of self-managing our single-family rentals, we decided to hire a property manager to provide full service management.

Implement documented repeatable processes to reduce errors and improve service levels.By being efficient, and cutting some of your costs you can hire better talent with the leftover cash. 

Could you get another tenant in the third bedroom to really bring down your cost of living?

Based on your description, Party 1 seems like the safer choice.

Just got the agreement and it's definitely a wholesale because part of it is about a 3rd party buyer.

Perhaps a nice 1950's built bungalow.Always hire a 3rd party property inspector to give you an unbiased feel for the home.

I have to say that the AIA system --- despite its flaws --- makes it easy for parties to work together.

That would be a helpful addition to your plan as you would further reduce your cost of living.Also don’t forget from that $600 you are planning on getting in cash flow you have taxes, insurance, maintenance, capex, and vacancy to consider.With two homes, you may want to keep that extra $20k as an emergency fund rather than spending it on a third property and then be left with no emergency funds.

When you’re confident in your numbers, you can negotiate with clarity and avoid being swayed by emotions.Understand the Other Party’s MotivationEvery seller has a reason for selling.

This will help you understand your options and decide if it's the right time to hire a pro.