If they are unwilling to consider offering mortgages for investment property should I look to a larger mortgage company or look for more creative financing options?

If there is some larger projects that are not a part of your $20,000 rehab budget, then thats probably right. 

I know investing in real estate is never completely passive, but from those of you with experience in larger properties like this, what types of situations typically come up that the owner has to resolve or become involved in?

You DO have to understand the process and be well-educated on what's going (your market, costs of the renovations, etc.).

.- Uncle putting 100% of (20%) down payment + some initial renovation costs down during purchase via conventional 30yr loan.   

That will allow you to A). make some mistakes with a lot more leeway than a newer investor starting now or have them work as investment properties at your basis where someone buying today would be cash flow negative or B) eventually sell or refinance the properties to raise the equity for higher return or larger scale investments.   

I would love to buy one to keep and completely renovate it and lease out to a business or possibly run the business myself.

To that point we began to look at larger properties in the 50-150 unit range.

We’ll be moving in shortly but first want to renovate the unit we’ll be living in.

There isn't nearly enough information on the calculator to give me a real indication of what is actually included in your numbers...but if you're planning for $35k profit...can you also afford to lose $15k...without experience it's possible to have your holding costs be much higher...and your renovation costs be 50% over if its your first project and you don't have actual contractor bids and are just guessing based on having read J Scott's book.