Hey Matt
I'm a fellow Iowan investing in the Iowa City area. My wife and I own an investment company (2 actually) and a general contracting/remodel company. We hold 50/50 interest in all companies.
I'll give you some of what I know although obviously consult your attorney and CPA.
First, as far as ownership, my attorney suggests using a LLC to hold real estate. He also suggests not holding all your properties in one LLC but rather only put 1 or 2 in a LLC and have multiple LLC's (assuming you're investing in residential).
My CPA suggests using a S-corp to rehab/sell properties and not to hold property long term in that corporation. (I assume you know the difference between corporation and LLC taxation?)
I think the point they are stressing is not to put all your eggs in one basket. Putting assets in several companies makes it difficult for people to access your assets if you are sued however, it also comes with more paperwork and associated costs.
Regarding becoming a contractor, if you are going to be doing much of the work and you have the skills, I would highly suggest it. There is no test in Iowa, only a $50 fee which can be waived if you do not have employees. You'll want liability insurance. What I do is have my investment company pay my contracting company to do the work on my properties. That way my contracting company is liable for the work. And it serves as my primary income.
Because my wife and I own the company together I thought about making her a majority owner in order to consider minority/women owned business grants etc but I really don't know if there is any advantage to that.
Although we never want to assume a partnership will end badly, it is very important to have a well written agreement in place spelling out details of what will happen in such case. (even with your wife or other family) Your attorney will help with that.
Marital status should not matter as you are simply creating a partnership.
Regarding financing, I use a commercial banker at Great Western Bank. They underwrite most of their loans in-house and are very flexible. If you purchase the right properties low enough, I've used bank financing and received a check at closing to do the repairs etc....
Otherwise get creative...
Good luck and ...
I AM NOT AN ATTORNEY OR CPA, NOR DO I PLAY ONE ON TV.