Portfolio expansion is really defined as an increase in cash flow. 

EVEN IF they could find qualified candidates to hire, do you think the people of Jefferson County are going to vote to increase their ad valorem taxes so the Sheriff's department can hire more deputies to serve more eviction notices for so-called rich investors?

If the cash flow on the existing properties goes close to breakeven, seems like you would be increasing your risk of large capital expenditures, like roofs or heat pumps, without cash flow to sustain them. 

That's a $20k increase in cost to the buyer. 

Also property taxes jump, fire insurance also increases... 

How much should someone increase their prices after adding such amenities or does it vary?

Additionally, exploring alternatives like legalizing the existing cellar apartment, if applicable, or renovating the current layout to increase rental income could be viable options.

Purchase price: $1,350,000 Cash invested: $150,000 Sale price: $2,200,000 We Converted a duplex to a triplex and increased rents by 150%.

The seller is saying that the lease expired years ago therefore there has been no rent increase.

Lot of condos being built for rental as well so rental income increase may not be as rapid.