OK, the first thing we have to talk about is domicile.
Your domicile is your true and permanent home. There is no single test to prove where your domicile is, it is a combination of many factors. You can only have one domicile at a time. It is possible for someone to move without changing their domicile, even for a long period of time. In addition, to establish a new domicile, you must also take active steps to abandon your prior domicile.
The Pennsylvania tax web site does a very good job of describing this, I was just there today for another question.
https://www.revenue.pa.gov/FormsandPublications/PAPersonalIncomeTaxGuide/Pages/Brief-Overview-Filing...
Once you have established a domicile in a US state, you are a resident of that state and you owe taxes in that state, even if you move around, unless you abandon that domicile and establish a new one somewhere else. Establishing a new domicile requires intent. If it is your intent to return to the Netherlands, then you have not established domicile in any state, even if you don't have a definite return date. If you moved to Georgia temporarily (such as with relatives) but your intent was always to establish a permanent residence closer to your job, then you never established domicile in GA but did establish domicile in NH. If it was your intent to live permanently in Georgia, but you had a change of circumstances and it became your new intent to live permanently in NH, then you did have a GA domicile even if was short term.
You will generally owe a resident income tax return in the state where you are domiciled, that pays income tax on your world-wide income, and a non-resident return in any state where you were living, even temporarily, for money earned while living in that state.
Also, you can be a statutory resident of a state even if your domicile is not there, if you live in the state more than 183 days of the year in a fixed abode (such as a home or apartment, but usually not a hotel).
Finally, I don't see any indication that Massachusetts will try and tax you. MA does not tax teleworkers, and you have never had a temporary or permanent residence in MA.
Now, you need to analyze your situation again. Have you actually abandoned your domicile in the Netherlands, or are you planning to move back? If you abandoned your NED domicile, did you establish domicile in GA? Did you then abandon your domicile in GA to establish a new domicile in NH? Or did you establish domicile in NH only because GA was temporary.
To give one example of how this plays out, let's say your intent was that the move to Georgia was intended to be temporary, you lived in Georgia less than 183 days, and you established domicile in NH on July 1, 2020.
1. You are not required to file a NH tax return because NH does not have personal income tax.
2. You would file a non-resident GA return, that reports only your GA-source income. Your GA-source income is your GA rental property, as well as all wages paid to you by any employer while you were living in GA. You will have to do this allocation in Turbotax.
3. The only reason you might owe MA income tax is if you travel to MA for your work, such as to meet in person with other members of your team. If you attend in-person meetings 1 day every 2 weeks, for example, MA will consider that 1/10th of your income is earned "in-state" and you would then file a MA non-resident tax return to allocate part of your wages to MA.
Other fact patterns would be analyzed following the same principles.
For your rental property, costs to improve the property before it is available to rent are not deductible on schedule C or schedule E. They are added to the cost basis of the property and become part of your depreciation expense once you place the property in service as a rental. Managing residential rental property is rarely a schedule C business in any case.
