However, it needs to be done correctly from the outset, I recommend using an attorney. 

I highly recommend taking your deal(s) to your local meetup.

Is one type recommended over another ?

I'd recommend a minimum fee like 10% and you charge interest and points that are equivalent to market conditions, you also get the first guaranteed 20% profit as the only capital partner. make sure to take title in a single purpose entity and dissolve it after you build.

Does anyone have brokers they would recommend working with for smaller (5-15 unit) apartment complexes in the Indy area?

It's unfortunate because it's a BiggerPockets recommendation Account Closed

Did you work with any real estate professionals (agents, lenders, etc.) that you'd recommend to others?

Also know that the housing market might not go up as quickly as you like...but honestly as long as it cash flows when you move out that is okay...I recommend saving up at least 6 months' worth of rents and having it cash flow at least $300 a month before moving out of the property.

As for the other recommendations suggested, I would have suggested the start with one unit but I would defer to local expertise and therefore fear @Jim K. is likely correct.  

I think you are making a bigger deal about this than it needs to be, and you could be telegraphing to your tenants to challenge/question the increase.Just send a diplomatic letter - no apologies, and I would not recommend concessions as that is antithetical to your balance sheet - detailing the increase and the timeline.