San Marino is an independent Republic, the oldest in the world, and it is not part of the European Union or the Schengen Treaty. However, regular entry into the Schengen area is also considered valid for San Marino.
There are several laws regarding residency in San Marino, and I think that those of articles 16-bis and 16-ter are the most interesting for the American entrepreneur who is married and has children under 25 years old:
Residence for economic reasons
The residence referred to in point 2) concerns those who start an economic activity in a corporate form with at least 51% ownership of the share capital. In the case of business activities in sectors to be incentivized, at least one permanent employee should be hired from the employment initiation lists. In the case of hiring a larger number of workers, including those hired for a fixed term, at least 50% of these must be hired from the employment initiation lists. If the business activity is in a sector not included among those to be incentivized, at least three permanent employees should be hired from the employment initiation lists. In the case of hiring a larger number of workers, including those hired for a fixed term, at least 50% of these must be hired from the employment initiation lists. The sectors to be incentivized are listed below. An additional requirement is the establishment of a real guarantee on a bank deposit or other financial instrument in favor of the Most Excellent Chamber, worth €75,000.00
Elective Residence art. 16-bis
This is a residence that is acquired through an investment in the Republic. To obtain this type of residence, one of the following two options is necessary:
Elective Residence 2020 art. 16-ter
Another type of elective residence, introduced in 2020, is that of art. 16-ter, reserved for those who: a) have never been fiscally resident in the Republic of San Marino and generate income outside of RSM. The duration is 15 years. The applicant must demonstrate that they have sufficient resources. Regarding income generated abroad, a substitute tax is due for the general income tax of individuals equal to 7% on the "net border" as defined by article 13, paragraph 3 of Law n. 166/2013 and its subsequent amendments with a minimum amount of 10,000.00 euros and a maximum of 100,000.00 euros for each fiscal year of the residence's validity. Until the consolidation of residence, the holder of atypical residence and secondary applicants: a) cannot access any type of dependent work relationship in the Broad Public Sector and in entities that, public or private law, are participated by the Most Excellent Chamber; b) do not have the right to receive benefits, grants, checks and public disbursements of any kind linked to the possession of residence, c) are required to take on at their own total expense the costs of health care, through private insurance or with the Institute for Social Security, in the ways established by the Institute itself, to cover all related risks.
Rules for movement within Italy and UE
Main rules for movement within the EU for residents of San Marino San Marino, while being a sovereign and independent entity, has a series of agreements with Italy and the European Union that facilitate movements between these regions. Generally, a resident of San Marino (with the obligation to reside at least 183 days in the Republic) would have the right to enter and stay in Italy or other European Union countries for short periods without the need for a visa. However, residence in San Marino does not automatically confer the right to long-term stay or to settle in a European Union country, such as Italy. These rights are regulated by the laws of the European Union and individual member nations. A non-European citizen residing in San Marino may need a residence permit to live long term in a European Union country. As for the issue of identity cards, San Marino issues identity documents to its residents, but these are not equivalent to a European identity card. Therefore, while an American citizen residing in San Marino could use the Sammarinese identity document to travel, living long term in another EU country, like Italy, might require additional documents or permits.