Leasing

I own a mansion and live in it. I own an apartment also, can I lease it out? If so, how?

There's an option on your property page, but basically anything below PI isn't worth renting out for anybody lol, your best bet would be to put it up for $1 for the merit then selling :)

Both of these pages are accessible from:  https://www.torn.com/estateagents.php

It's best to use two browser tabs to accomplish this.

Open Your Properties: https://www.torn.com/properties.php

Open the Rental Market:  https://www.torn.com/properties.php?step=rentalmarket

In the Rental Market, select the property type you're trying to lease out.  This brings up a list of all properties of that type.

In Your Properties, select the property you're trying to lease out, and click the sign post(Lease this Property).  This opens the Property Detail to the 'Lease' section.  Click "View Property Info" and note the Happiness.  For this example, I'm using a 2600 Happiness Private Island.

Switch back to the Rental Market, and move down the list until you find properties with the same base Happiness.  Note the range at which these Properties are currently listed for lease.  The cheapest such Properties should be toward the top of the list.  For my example, 2600 Happiness Private Islands are offered for lease at 395k per day right now.

Returning to Your Properties, depending on the price point you want to hit, you can try for 100 days, or you can try for a shorter duration(with potentially more profit per day).  I'm going to list this one for 100 days at 380k per day(38 mil).  Select "Add Property to Rental Market" and enter the appropriate numbers.  In my case, this is 38 mil and 100 days.  The game only lists the cost per day in the actual listing; you will need to do the math to figure out what your total should be based on your target daily rate.

Alternatively, if you separately arrange for a lease with an individual, you can use the "Lease this Property" tab here to offer the property to lease to a specific person.