My wife and I have loved real estate for a long time and invested in other areas, but are focused on building our portfolio in Kansas City.

They build on site.One thing you mention is construction costs. 

Who said you need to build all 6 cabins at once?

The GC can handle the entire project, coordinate different subcontractors and make sure the project is completed per building codes - especially if the rehab is complex or involves multiple trades like plumbing, electrical, and carpentry.

A buddy has a 5 unit building he needs to sell at 475k.

Its also a good idea to build relationships with realtors, contractors, insurance agents, real estate attorneys, and property managers in your area so take advantage of events, conferences, and meetups.

Assuming the Oakland rental market continues to remain stagnant/competitive with newer buildings going up, is property appreciation the only way to increasing wealth with my building?

Quote from @Justin Jefferson: Hi my goal is to also create ownership and build my assets for the future.

Purchase price: $355,000 3 unit house hack with 2 separate buildings. 3 Bedroom/2 bath, 2 bedroom/2 bath, 1 bed/1 bath.

.- Your maintenance and repairs will be mostly limited to the interior of the property as the condo management will maintain the building- You won't have to worry about tenants maintaining the grounds around the buildingCons:- Condo fees may change drastically over time and it's largely not in your control- Condo bylaws can be tough to work around.