Contractors, brick masonry experts, structural engineers, home inspectors, lenders. 

He did a book for Bigger Pockets, but by large Bigger Pockets is not so pro Sub2 so not sure why they allowed this other than he is an expert at self promotions, etc..

A legal expert might correct me here.

Need help with ROISingle FamilyPurchase Price - 260kTaxes - $10kRennovations - $30kRent - $4k/monthARV - $400kIf I convert it to multi family - 4 unitsPurchase Price - $260kTaxes - $10kRennovations - $110kRent - $5k/m...

So get the lay of the land but always rely on a local market expert to help guide you.First let’s get a basic handle on the Kansas City metropolitan area.

Use a reputable expert like @Dave Foster and you’ll be covered.

I understand as someone new to real estate investing there is a lot to learn and even though I have read many books, until I do it myself for a few years, I will be far from an expert.

Connect with local real estate agents for expert advice.Good Luck! 

Not saying I'm an expert in all of this but, this talk of rising rates and Due on Sale being called in just doesn't make sense. 

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.