I know the simple concepts, blocking and tackling, but I’m guessing there are other ways to achieve the goal faster.  

This gives me more confidence to tackle a flip. 

;)   I love that you aren't afraid to tackle big problems, and seem to keep a level head when many investors would get super stressed out and want to cut their losses (hence 3 owners in 10 years!). 

Sounds like you have the right experience to tackle this. 

Structurally it looks as it should have some sort of additional support.My question is as a semi-experienced rehab and DIYer would this be something you would suggest tackling myself, and if so what suggestions would you have for fixing it?

The Mayor of L.A recently stated he would like rent control to apply to newer units too .He also recently expanded RSO with more "protections " for tenants .https://www.lamayor.org/mayor-garcetti-continues-tackle-housing-crisis-new-law-strengthening-rent-stabilization-ordinanceIt seems everytime a landlord wants to develop their property the tenants are now suing.. even with the relocation payouts being $6,000 plus per tenant .

Hello All...I am looking at a 16 unit that is completely vacant..anyone have experience tackling a completely vacant apartment.

It's just good blocking and tackling that's useful in every business.Keep good communications with the tenant.

SPECIFIC instructions for each sub and check behind them and in front of them to make sure that they did what they were supposed to do, and that the site is 100% prepped for the next man in.This means that you really need to have a functional understanding of what's involved at every step in the process... otherwise, frustration and misery will be your lot in life.If this is your first or even second rodeo, you might be better off hiring someone to do the management for you, and watching what they do before you try and tackle it yourself.Word of caution - beware the handyman who claims to be able to do "absolutely everything"... houses are complicated products, and I personally don't trust someone who claims to be a master at every aspect of construction.

Three key skills (among the many) will help anyone get started...As a rehabber or fix-and-flipper, building a buyers list is probably the first task to tackle.