Maybe we need a few more details. I'm not entirely clear on the situation with the house. Now it seems like the house is in Italy, is that true? And is it worth $400,000 USD or $350,000 Euros? Those are very different amounts.
You're currently in the US, in New York, correct? How long do you plan to stay there? Do you plan to return to Italy when you retire? Where are you currently living? In an apartment? Do you have roommates?
If the house is in Italy, and rented to someone else, and you live in New York, who's managing the property? Who's paying the utilities and taxes?
If I were you, I'd sell the house, move the cash to the US, max out any 401(k) and Roth IRA contribution room I had, invest the cash in low-fee index and bond mutual funds, keeping 3 month's expenses liquid in a high-interest savings account.
I also think more details about the house and yourself might be helpful.
I can understand that selling the house might not be an option for emotional/family reasons. So, you will keep it. Is the $950 per month you receive net or gross? How stable is it? Have you had the same tenant for 8 years with the expectation of a long term continuation or is this something that takes a lot of ongoing management?
In my thinking, whether it is worth 350 keuro or $400k is irrelevant if you won't sell it. To you it is a source of cash flow. What is the monthly net cash flow from the property?
What is your tax status? Are you subject to US tax laws or do you pay Italian taxes? That could make a huge difference if you plan to retire to another country.
You say you are an accountant. Are you a CPA or similarly skilled/licensed professional who could conceivably earn money consulting? Or are you a bookkeeper? Because improving your credentials so that you can earn money consulting might be an important part of achieving your early retirement dream.
Are you married/partnered?
There is another blog/forum called "extreme early retirement" that you might be interested in. I have no affiliation, I just think you might like it.