It was hard staying positive especially when unexpected repairs came up, but we stayed the course.

Ignoring the issue of trader income not being eligible, the entire $57,000 Solo 401k contribution could be structured as employer's contribution (with compensation high enough) without employee deferral component. 

Some Turnkey Providers rehab correctly and look at all major components so you don't have any Capital Expenditures (CapEX) for a pre-determined amount of time. 

If you put your rehab budget into each of these, would you be able to get it all back if you need to sell unexpectedly?

That part if pretty straightforward, especially if you speak with a good lender, but I'd say most important is to make sure you dont drain your cash at closing--you want a good chunk of cash left over to protect yourself from unexpected costs (I bought my first multi when I was 23 and within a month had a furnace go out). 

If the after reno value is $600K, and your contractor figures $80K (add in extra for the unexpected), you still have a lot of room for profit if you sell it. 

Not only will waiting a little while allow you to work on your credit, it will also allow you more time to save up for a down payment and additional unexpected costs. 

Then an unexpected HVAC replacement put me over budget What made you interested in investing in this type of deal?

As a result gain is calculated in chunks.There is also an interest income component every year.In general - you should have the seller consult his/her CPA.

We also addressed some of the major components including replacing the roof and upgrading the external tankless water heater.