Every rental is like receiving a raise.

@Immanuel Sibero I suppose I thought of it more in the context of there was a new property to purchase and capital needed to be raised from refinance or sale, thus you would need to compare your own properties against one another, to determine which to sacrifice for lack of a better term. 

It recently came to my attention that Upper Darby is lobbying for raising the yearly rental license fee from $86 per property per year to $135 per property per year.

I was also raised in Bakersfield, hence Bakersfield over Fresno or another equivalent central valley city. 

Presuming you have a descent NOI on the property that would support a very occasional $200 expense, and you aren't worried about starting some sort of 'trend' with multiple tenants suddenly complain to get a new appliance, why not try and swap it out and appease the tenant.You win in more than one way... (1) the tenant quits complaining / you get peace and quiet, (2) when you raise their rent the next time they feel like you listened to their concerns and took care of them, etc (you buy some good will).  

What is the best way to raise 40k to finish the job?

Raise the rents to market values and rehab to force equity and sell in 2 years to avoid capital gains.

What are you raising money for?

I will definitely raise the rent at the end of their lease.

That type of exponential growth has put enormous pressure on the market, raising the median home price from $193,520 in 2010 to $318,000 in 2019.