It definitely seems like a much bigger project then what a newbie should probably be undertaking.

If you have the cash to go up to 4 and 5 units, you will find less competition as most house hackers are on 2 and 3s, but it's also a big undertaking to do that many units as a new investor.

With such a big undertaking I'd really like to interview a few builders to compare. 

It can be a big undertaking, although there can be profit in it IF the numbers are right and IF you have done your homework to know what you are getting into (both big “IFs”).

We currently are in the very early stages, (We haven't been into any of the properties, only talked to realtors and agencies about the properties and the process of the undertaking) While we are scheduling the walk through of each property for the next few weeks.

Is your plan to undertake more of a DIY rehab to start or is your bandwidth too limited? 

@Rob Carmody I believe it's safe to assume that your employer does not want/allow employees to undertake the activities, not doing the activities with a license.

It may not be a minor undertaking. 

HahaThe major undertaking and something I hadn’t done before was a basement remodel where I added ~500 sq ft and an additional bedroom to 1 of the units, making it a 3 bed/1 bath.

Not sure what a 6 unit would require you to do but it is a significant undertaking.