I would appreciate any advice on whether it's a good idea to invest in land on a slope and the potential challenges of building on such terrain.If this seems like a worthwhile investment, can anyone recommend reputable construction companies that specialize in cabin builds on slopes? 

All complimented with Amazon fulfillment centers, google, and more tech manufacturing jobs.The bad reputation of “Detroit” comes from OOS investors wanting sub $40,000, D class properties in poor condition, because they pencil out to 2-3% deals on paper.

I leverage a cleaning service, a few landscapers, handymen, contractors and plumber.

I hope you are asking two separate unrelated questions, because there's no point in doing cost segregation for properties held inside your self-directed solo 401k, save for some very rare exceptions.Some of the Bigger Pockets experts who operate reputable costs segregation companies are @Bernard Reisz, @Yonah Weiss and @Julio GonzalezSome of the Bigger Pockets experts who offer Solo 401k administrator services are @Dmitriy Fomichenko, again @Bernard Reisz and @Brian EastmanReach out to them and see if they can help.

A $3m purchase price home was certainly not bought by a plumber, right. 

Do i t to build your online presence, reputation and credibility as a business.

With that said can anyone suggest reputable lenders that are able to assist me with a debt consolidation loan of ~25K?  

If the company is reputable, I don't need to vet the company.

I personally know several blue-collar millionaires from HVAC techs to plumbers.

Next we discussed how we would try and change the structure of our current plumbers/electricians.