When I looked into IRA accounts, I found that it didn't do service to my situation.

Whether you need a CPA with just three rentals depends on the complexity of your situation and your comfort level with DIY tax prep.If things are pretty straightforward, you might be fine with tax software for now.

We are targeting a 'house hack' situation where 50% of the units would be rentals, and above 50% would be our own 3LDK for family home...

Additionally, regarding the legal structure, an LLC seems to be the most suitable option for our situation.

Right now, we're a bunch of strangers commenting on your post - we don't know your background, financial situation, W2 job, lifestyle (single, married, kids, etc), risk tolerance etc (not that you should share all that information on a public forum). 

If you provide any kind of substantial services like catering, car service, etc you will change you tax situation and no longer can file under Schedule E.

In your situation there is actually another factor that may work in your favor.Only the proceeds allocated to the sale of the building can be used in a 1031exchange. 

And because I'm looking for a long term finance situation, I'm not looking for a loan that is going to have a really high interest rate, with hopes of refinancing later.

Dealing with warranty service is a pain in any situation but when you also have to deal with a tenant on top its even worse.

If a landlord plans to hold the property for a while, we always recommend an annual lease, ending to align with the summer leading lesson, or staggered with their other leases depending on the situation.