Things like theory, title, escrow, valuation, taxation, financing, possession, legal aspects, business models, leverage, etc.If you can learn these independently, more power to you.

When it comes to details around financing, regulation and taxation, much of the information is U.S.A. specific and those of us from elsewhere need to find local information sources to supplement.  

That is primarily why I wanted to reply and understand further.I know that one of the biggest problems with 401k loans is job security, as the note will become due within 90 days of a job change, or the balance will be treated as an unqualified distribution (and taxed and penalized).My question is regarding the double taxation issue; I think 401k loans are generally considered last resort options because the money is paid back with after tax dollars.

Assessed value is worthless and is for taxation purposes only.

Im wondering if corporate holdings are like personal holdings, where if you hold a property a year you avoid the short term taxation.

That doesn't make sense as it wouldn't be over the threshold to tax at 20 percent.

I want learn if there are any tricks like lower taxation, or incentives in some states.

According to the Ohio Department of Taxation, "every nonresident [of Ohio] having Ohio-sourced income must also file."

@Derek BennetsenTo clarify, a Solo 401k is specifically exempted from taxation on Unrelated Debt Financed Income (UDFI) when the plan acquires real property using a mortgage.  

None of the common softwares out there do this automatically.A C-Corp can be a good structure, but it does come with a lot of other headaches as well as the double taxation issue, so make sure this is really the best scenario for you before you head down that road.