How can I increase income from this property? 

You can increase your NOI by either increasing revenue or lower expenses.

I was just thinking how to increase the ARV to the highest I can.

Secondly, wholesaling is simple to learn but not simple to do.

Believe me, if it were that simple everyone would do it and we wouldnt have many employees left.

Currently, about $1tril is spent on interest payments, and even if rates stay current, that will increase, since debt is increasing.

A simple business checking (Using your LLCs EIN), a business savings account (For CapEX, vacancies, estimated taxes, etc), and a business credit card for expenses would be an excellent starting point!

Because they are undermarket, most mom and pop or uneducated 'investors' will just see it for what it is, maybe they'll run some simple numbers, and ofcourse the numbers with the below market rents and the now new purchase price don't likely pencil out and so... they will walk away and keep looking and are usually the ones complaining that 'it's hard to find any good properties in today's market'... where in fact that is exactly where you as a savvy investor make your money. 

Sustained maintenance costs that are higher than anticipated increased occupancy and nightly rates.

With strategic upgrades and modernization efforts, these properties can be transformed into sought-after residences, thereby increasing their value and rental potential.LOCATION, LOCATION, LOCATION – These Condos are often in prime locations in established neighborhoods, providing a sense of authenticity and charm that appeals to both residents and tourists.