I know how frustrating it is to work so hard for something only to lose it, the knowledge or techniques to become out of date and to feel that you have lost your 'edge'.

Multi-family properties allow you to employ several different investment techniques.

This is more a matter or technique and quality of workmanship than anything else. 

Study up on tenant screening techniques, and implement them diligently.CRITICALLY IMPORTANT: Too much noise & too much mess are the two most common problems you’ll have with housemates, so be pro-active in preventing those problems before they occur.

Both drywall and paint are very easy in theory/concept, but hard to get right if you don't have precise knowledge of the techniques.

@Rose Ganor No... you pretty much got it...You could try some of the "influencer's" techniques, and similar techniques taught by real estate investors. 

These techniques, while still doable today, had its heyday in the 1970s and early 1980s when double digit interest rates combined with no due on sale clause accounted for the majority of real estate sales activity.  99.9% of loans are such that the lender wants to know the source of the down payment.  

According to my research a capital asset is:The IRS indicates what constitutes a real property capital improvement as follows:Fixing a defect or design flawCreating an addition, physical enlargement or expansionCreating an increase in capacity, productivity or efficiencyRebuilding property after the end of its economic useful lifeReplacing a major component or structural part of the propertyAdapting property to a new or different useA repair is as follows:Improvements that "keep" property in efficient operating conditionRestores the property to its previous conditionProtects the underlying property through routine maintenanceIncidental Repair to propertyReference is http://www.dbbllc.com/newsletters/focus/mar2012/irs-clarifies-capital-improvement-vs-repair-expenseNext time I will rent a small excavator, dig my own hole, and put on a Fernco.

@William PaxtonWhat were the big takeaways from the course and what techniques does he teach?

My best recommendation here is to get with other investors in your market and ask them what techniques and companies they are using for foundation work.