I've done several 1 for 1 exchanges, trading a SFR for a triplex or a duplex for a fourplex.

This would mitigate your tax rate and quite possibly lock in some solid gains from your stock gain while averting what may be choppy trading coming down the pipe. 

As your rental portfolio grows you should look into getting a property manager so that you won't be constantly trading your time for money

Timing is much harder and especially just starting out, finding a property where the numbers work will help build the experience and you always have the option to trade up via 1031 for a multifamily property in the future.

I have heard a lot stating to find your niche and stick to it, so as to not spread yourself too thin and become a jack of all trades rather than king/queen of one. 

I’m a structural fitter and welder by trade with a background in cnc machining and general construction.

I worked there for 2 years and wouldn't trade that time for anything.

Their depreciation does NOT start all over again, but by trading up in value they have acquired additional cost basis that can be depreciated. 

The issue you have with mutli-family in places like Palatine is that the availability is very low, so they trade mostly off-market and are passed down to families.  

Many of the older investors on BP would trade places with you in a nanosecond.