It depends on the specific deals and terms.

This is common during negotiations for proposed business collaborations for projects, mergers, acquisitions and selling of a business.

I've only heard about NARPM here on BP; which isn't saying a lot.I agree that NARPM might not be the primary avenue for growing your business through referrals.

Also, Ive bought office supplies, went out to eat with contractors, and more, should I be using a business credit card? 

Unfortunately, the majority of investors that experience terrible service from turnkey companies, figure out that it's not worth spending tens of thousands of dollars suing their turnkey provider and just move on - which allows the turnkey provider to not change their ways and stay in business:(You should also check out this BP thread about the topic:https://www.biggerpockets.com/forums/88/topics/976647-turnkey-company-suggestion?

Generally any multi family purchases 5+ units is considered commercial, and although many lenders offer financing, the down payment requirements will be slightly higher..usually 25-35% depending on the number of doors.  

It depends on one's financial strength, the quality of the property, how many properties they own, and other factors.I like to start with one significant expense and three months of vacancy.

You are not scrambling to get 4 units filled at the same time  You can definitely ask for it to be vacant but it will depend on what the lease say.

I am one to give people benefit of the doubt but it usually ends up with hurt feelings and regrets in business.

My business partner has purchased large parcels of land, but never developed homes.