However, since I've been doing part-time real estate investing the past few years, I continuously hear about how finding "good" deals today is hard, but once you find a "good" deal, getting financing is "easy".   

But Boyfriend continued to make monthly rental payments.

I would like to continue to invest in rental properties for a long period of time and buying a turnkey property wouldn't allow me to gain experience as far as owning and managing rental properties.

These repairs were inline with the work that was previously done in 2008 and 2012 by a separate company.Now here is the funny part...The seller and the seller's agent both believe the home doesn't have any foundation issues because of the engineer's letter despite the visible damage and the home inspection and the pier company's investigation. 

The property would serve as security for the loan and all payments would flow back to the solo 401k plan and continue to maintain their tax sheltered status.

I don't want to continue to show a loss but I also don't want to take a major hit come tax time. 

Given that there is a possibility that I may have to tear the walls down, does anyone think it's worth it to continue to invest in this rehab property?

If I didn’t need the money I would tend to hold, not for the cash flow but just because an asset in SD is so valuable and hard to buy again, long term it will likely continue to appreciate.

This is critical to your continued success if you are new to investing. 

@Robert DelVecchioI believe that on Zillow under "Price / Tax History" it will initially list the price the house is for sale, then when an offer is pending Zillow will add a line that states "Pending" under "EVENT" but will continue to use the initial list price under "PRICE".