Yes, you can buy any properties and sell whenever you want, as long as you buy in CASH.
For some loan, depends on the loan, you might be able to, now, that you will need to talk to Loan Officer and he/she can tell you. There are flippers who does that but most of time, they use private lender.
You don't have be a citizen to buy a properties here in US, but there are some laws and reqirements you will have to follow and that is different by State to State.
Of course, when you sell, you will be TAXED for sure and will have to pay more if you are not citizen of USA.
For more in depth info, you will need to hire an attorney to get legal advice.
I hope this answer gave you some help.