The IRS doesn't care if you are paying back a loan with the proceeds or buying a yatch.

C-Corp has funds for REIObviously, there are rules, it is the IRS afterall, but for me tapping some IRA money was better than a HELOC.

Also funds used to further improve or repair the property.The portion used for other investment can be deducted elsewhere in your returns.The portion used for non-investment isn't deductible.Keep in mind there are IRS tracing rules.If you already knew all this forgive my off-topic comments. 

It is also true that these are hi-stress, hi-hours required as they are IRS classified as Exempt Employes and thus work for fixed salaries w/o OT.

I can then categorize them (accoriding to IRS rules) and tag with different houses or even send them to separate house expense reports.

Many tax defaulted properties have weed abatements, IRS leans, or are contaminated.

Some people have made bankruptcies or IRS liens their niche'. 

They are also built in an controlled environment.But the one thing that I've found as a developer for the past few decades is the minimal amount of theft and vandalism realized with HUD or MOD installation and the very short amount of time you spend on a job site overall compared to a slow and tedious sight/stick built process.Cities and neighbors love you when there's not a bunch of trucks filled with dozens of people showing up everyday for months on end with their loud, gruff and profanity laced conversations, jokes and laughter along with loud hip hop and or rap music blaring away all day for months on end.About the only noise involved in the entire process is the heavy equipment used to excavate and prep the site.

Do I need to register with the irs (itin #)?

For whatever reason, siblings are not disqualified parties per the IRS guidelines.