Heads in beds means more revenue.

As for other amenities, some crowd-pleasers that won't break the bank are coffee maker + starter pack of pods, basic workout equipment (yoga mat, resistance bands), phone charging stations by the beds, and basic kitchen essentials like olive oil, salt/pepper, coffee filters, etc.

My current tenant has removed a picture from the wall and replaced the provided bedding with their own belongings. 

My mom does not owe anything on it.3)It is well kept, 2 bed 2.5 bath, fully furnished.

I just was giving a rule of thumb (framing was what I was bringing into the convo adding sf/adding bed/bath etc. without stating framing).

But I could easily make this a 3 bed, 2 bath within the existing sq ft. 

The unit consists of two beds, one office and one bathroom.

This is for a 3 bed 1.5-2 bath house around 1500sqft.Im in Philly area

.: Quote from @Alberto Cioni: The ADU unit construction here is around $ 200K-250K for 2 bed and 2 bath.

It is a side by side duplex, both two bed two bath units.