For example, if we got a $100/mo raise (after tax), we might increase our monthly expenses by $50.   

Over time as my cash flow and income increase it’ll become easier and within 5 years of starting I should be buying 5-6 properties per year.

Especially with only 15% down.I've been seeing 10 year interest rates creeping higher and higher above 5% over the last few weeks.   10-year Treasury is at 2.77% today, so even 5.10% is only ~230bps.   30 year amort is also becoming increasingly scarce on smaller deals.  

Perhaps fix up a couple units, increase rents, live there for 1 year, then move on to the next multi family.

In a rising market, I personally wouldn't want a 3-year lease - unless it allows for incremental increases in rents during the lease term.

NPV gives you a dollar figure that represents the increase  (or decrease ) in cashflow for the term of the investment. 

@Tamara Smith Short term rentals can be a great way to increase your cash flow, but be careful about the specific locations you choose as the laws for each municipality are different.

Those where the rent has increased but the value has not, hold. 

House hacking allows people to start this journey in their own home and increase leverage through FHA and other low-down-payment loan options.There is nothing stopping you from just buying a rental property.

If you are speculating on appreciation this may be the wrong time to get into the market, you will need cash flow to survive.Your best investment oportunity will come from multi unit properties with the use of leverage to increase returns.