Less than most buyers expect. The core requirements are a valid passport, funds that can be documented and moved into the United States through normal banking channels, and, for most transactions, a US bank account to operate from during the purchase. No visa category or residency status is required to hold title.
If financing, lenders will ask for more: bank references, proof of income or assets from your home country, and a larger down payment than a domestic borrower typically posts. If paying cash, the file is mostly about documenting the source and path of funds, which US banks and title companies are required to verify.
Buyers renting out the property or selling later will also encounter the US tax identification process. The sequence is well worn: Rangely can map the checklist for your specific situation, in English or Spanish, and connect you with lenders and advisors who work with international files daily.