The lender will want to see that the income generated by the property can cover the monthly principal, interest, taxes, insurance and HOA (if applicable).

Next applicant...

What is the safest way to store the money and keep it liquid?

Cash flow may not be positive after accounting for other expenses like your annual property taxes, insurance, and mortgage payments if applicable.

I am looking to get something like a Termidor application done.

I recommend your purchase agreement include an opportunity to review any lease agreement, payment history, and application screening for current occupants.

If you can, go several times, so you can watch it happen from the foundation all the way up.If you live close to a store like Home Depot or Lowe's, sometimes they have free classes on "how to install a ceiling fan" or "how to paint". 

I specifically need really user friendly accounting features (including ability to sync with quickbooks and print checks directly from the site/software), customizable online application, and online rent-pay as an option (hopefully with free or very cheap ACH). 

A few examples of when you might see a higher cap rate is a non-credit tenant (mom and pop, one store operator, hand to mouth financials) or you might see this with a tenant whose lease term is set to expire in the near term (2 -3 years or less).

Most are actually pretty helpful if you reach out and ask questions in advance vs being hostile when they make you jump through hoops completing applications and preparing for the P&Z hearing.