It will be OK. Fully clean it out, and vacuum the inside. Put the floor mats in the trunk. Hang an air freshener on the mirror.
Unlock it. Take the battery out and put it in a basement or heated garage, put it on a piece of wood, not directly on concrete.
Do not put where it can damage anything in case it leaks, like in a carpeted closet. You can buy a trickle charger or say in 45 days take to an auto parts store for a full drain and slow charge. The major chains in my area will do this for free.
Make sure the oil is topped off. Top off the coolant.
Find some way to put air in the tires as needed. If you let them go flat and sit they will be ruined, ie dry rot, or the sidewalls will be damaged.
Leave the parking brake off and chock the front and back of at least one wheel.
That is about all you need to do.
What is the make, model, year, and miles?
Do you know what is specifically wrong with it? I have seen mechanics say...Blown engine....and they are just guessing, and not doing the diagnosis.