I am considering getting into this space (looking at some courses), but worried that its too late, and that deep local market knowledge/understanding of buyers/connection with developers etc is required to make this work, which only incumbent/long term investors will have and would be hard for a new entrant starting from scratch to catch-up...is my hypothesis valid in your opinion ?

These types of properties require experienced management to navigate the challenges effectively.

I'm not sure if the program is still going on, but has definitely revitalized a lot of the area when it was once destined to follow the way of other older cities that are aging out of existence both in terms of people and property. 

although I'm skeptical of going with her service, it is pretty logical because she would be helping me rent out a property long-term but sublease it for Airbnb.

Flipping, renting, or sitting tight for long-term appreciation-there is potential for anyone willing to do the work.

For example: We provide tax preparation and advisory services to people who invest in commercial (including multifamily) real estate, and high w2 earners investing in short-term rentals.

That's why mature investors with long positions like Boston while places like Brockton and Holyoke are more affordable.

The sooner you regain control, prove that you fully intend to enforce the terms of your lease, and that you will not be 'played' by their recall of events or documents, the more effective this action will be.  

Long term intelligence of this move is to be seen. 

All a mid-term rental is someone staying not permanently but longer than on vacation.