If the latter, as others have mentioned, best to get that paid down/off first before looking to invest.And totally on board with the Dave Ramsey plan mentioned by @Steve Vaughan.

@Greg Scott, I should have mentioned that window units are really common in my city. 

@Hadar Orkibi as I mention in my post I currently have a mortgage on my personal home.

The mentioned potential fines and told us even if we did demo/replace ourselves then we'd still need a lead test at the end of the reno to get a lead cert and if we missed even one spot they'd need to abate and clean the whole house, leading us back to square one. 

@Chatree C.You will need to find a Solo 401(k) plan document provider and then you can have the funds reside at the custodian that you mentioned or at a local bank if you prefer.The Solo 401(k) provider will also assist with the ongoing compliance requirements such as filing form 5500-ez when needed, processing plan updates and  also answering technical questions regarding the rules and regulations.Regarding UDFI, this tax generally does not apply to the Solo 401(k) plans.

So I mentioned the 50k comment moreso so you understand where we are at currently.

They are very flexible and thus ideally suited to the types of strategies I mentioned above.

In the home inspection report there is no mention of this valve ever being looked at.

If nothing more than you putting yourself out there as available to participate in the areas I mentioned above. 

...where do you go to find these nebulous "market conditions" articles always mention but never go into how to analyze them?