Says the humidity is 60% so she bought a dehumidifier and odor eliminator plus activated charcoal to help with the smell.

The service fee or cost can be justified in saving time (and mortgage payments) during the application and approval process.

Or is that considered a “hands off” activity and not taxable?

However, lower down payments typically result in higher monthly payments and PMI, so it's best to explore various options and consider all associated costs.If you decide to rent out your current home, consider whether self-managing the property or using a service would be the best fit for you both.

You can never be everything to everybody, but you offer a service that someone, somewhere wants. 

Different investors swear by different criteria, whether it's IRR (and the closely related NPV), cash on cash, the debt coverage service ratio (DSCR), the CAP rate for a property, or some other metric.

Now, for comps:  the only way to get comps here is to be a realtor (which they pay for access), or an appraiser (and they pay for access as well), or to pay for access through one of the servicing companies that provide this. 

Please consider factors like price, location, product variety, customer service, and brand loyalty.

In fact, providing substantial services changes STRs from a rental activity to a business and triggers self-employment taxes on the net profit.

The best source may be to call active listings as well.