The first deal is the one you are more likely to screw up (because of inexperience).

While getting a management company as you scale is a great idea; managing your own properties for a time gives you insight and inexperience into this portion of the industry; which in turn gives you much more insight into what your managing company does, provide them with better feedback, and gain a better idea of what questions to ask them during screening.

It speaks of inexperience rather than intention. 

I have done over 10 residential deals but this was my first multi unit transaction so I was pretty inexperience and didn't know what to expect.

Lastly, don't let age or inexperience delay you.

Do I as an inexperience party partner/get mentor by more experience folks, and perhaps I'd put down more money or the mentor gets larger split?

Inexperience isn’t a bad think, just understand that there is greater risk.

I have been studying this space over the last few months and a lot of GPs rely on the ignorance of investors (about their failures, inexperience, unrealistic underwriting assumptions or their unreasonable fees) to take more people's money. 

If they’re giving you a hard time about it, then the only mistake I would say you made was working with someone inexperience enough to understand that stuff happens.

I am certain they are out there, but due to my inexperience I'm just not finding them.