No. The Highrise Terms of Service say you may not share, sell, transfer, or otherwise let anyone else access or use your account. The only exception is a parent or legal guardian of a minor.
Can I buy an account from another player?
No. Buying an account breaks the same rule, and the original owner can still recover it. Support can't help if a seller doesn't deliver, takes the account back, or the account is recovered by its creator.
Can a friend play on my account for a while?
The Terms call this piloting. It isn't banned, but it's strongly discouraged and entirely at your own risk. You're responsible for everything done on your account, and Highrise offers no protection or recovery for what happens while someone else uses it, including lost access, items, Gold, or account standing.
What about selling items or Gold for real money?
Trades in Highrise use Gold and items inside the game. Selling items, Gold, or accounts for real money outside Highrise breaks the rules and can lead to action on your account. See How do I appeal a ban, mute, or warning? if that has already happened.
Someone offered to buy my account or asked for my password
Don't share it, and report them from their profile. See How do I report another player?
Where can I read the full rules?
Read the Highrise Terms of Service, section 2, User Accounts.