I assume so, but I want to make sure here.How should I structure the deal with my father so that it's professional and makes him money, assuming a positive outcome on the flip?

This is something that a tax attorney who specializes in ERISA law and has specific knowledge of self directed IRA LLC structures will be aware of and able to advise a client on.  

Also, I have a few friends who are interested in investing in real estate with me... how would/could you structure a deal with them given the situation described above based and based on them investing 25% to 40% of the asking price?

I'm not saying its not possible to have structural damage, just that its not as likely as you might think since you walk underneath the tub every day and can see the signs of a leak before it gets out of control. 

I separate structure bid and truss bid. all my rfq and rfp are like that.

What do you generally do in poor soil conditions ( if you have run into this.... ) a structural basement, or crawlspace?

My previous secretary manages our "production" lines, aggregate production, motor shop, and supply chain, then she graduated to 3 projects (20-30 people per project) doing it only by phone and bi-weekly reports and one foreman meeting each week, but those are more easy, just doing roads and small structures like drains and ditches.

Who do you structure your business if you are planning to do most of your investing in the states?

Note I'm not contemplating repairs / maintenance type stuff, such as sewer mains or 1) Moving a home to a new location (as in so expensive you're nuts to contemplate it)2) Replacing / significantly changing external look / structural elements / adding a story3) Replacing vinyl siding with full brick or stone all the way around4) Replacing old heating (baseboard radiant) with new, such as a heat pump and forced air5) Updating Kitchens6) Updating bathrooms7) Replacing floors (like carpet to hardwood or stone)8) Updating fixtures9) Painting

If you're testing the waters, just buy adequate insurance to protect yourself until you have a proper legal structure.