Let me know if you need some good options here; we work with quality accountants all around the country.   

If they don't - then it's optional.  

Most tax software has an option to specify that rental income is non-passive, and that's how you do it.

However, those two options are too pricey for me.

I might do a deal where I purchased the property and provided the “buyer” worth an option to buy for the period of the loan with monthly rent” payments equal to the interest payments on the would be note.  

The art is to increase the rent without running off GOOD tenants (very important, if the tenants aren't ideal tenants then non-renewing becomes the default option).

Are there options for assuming the existing mortgage and financing the remaining balance with another mortgage?

Current lien holder is going to be pretty much your only option. 

I would have moved there but with Grand kids all on the west coast it was not an option.

Unfortunately, you have to call these OTA's many times over until you get a customer service rep who sympathizes, is knowledgeable about the platform rules and is willing to actually help you.If you don't want to ride it out, i think you have options.