Hi @Emily De Leon,
It's not the classic definition to house hacking (that usually involves multifamily), but you still have a "tenant" paying for a portion of your primary residence mortgage while allowing you to keep the property and at zero cost to you so, sure - why not. :)
As for tax benefits, it gets a little tricky as to how you are claiming the condo on your returns. Assuming that (since it's been your primary residence) you have both been claiming it as a primary residence with everything being split down the middle (mtg interest, property taxes, etc), then on your tax return you could switch from claiming it as a primary residence to claiming it as an income property. This would allow you to take the rent you receive, and apply it to half of the expenses plus allow you to start taking half of the depreciation. This would most likely generate a paper loss that is tax beneficial.
If you want your sister to also realize the benefits, then you'd have to figure out what part of the house is rented and what part is lived in. So, since it's a 2/2 let's say 50%. Your sister would take half of everything and claim it as 'owner occupied'. The remaining 50% could then be split between the two of you by converting 'half' the house into a rental. It's essentially the same thing as before, just that you are both splitting the business side, and she's also getting the owner occupied deduction. You'd lose your owner deduction though (at least if you did this by the books).
There could be some other benefits if you put in an LLC, but since your sister still lives there - I wouldn't advise that.
I'd go with where she claims half of it as owner occupied on her return, you claim half of it as investment, and then maybe you put your tax savings from the loss into that cosmetic repair fund. You keep monthly profit, but you both reap in the tax savings without making this difficult.
Another advantage of this is when there is a repair or upgrade you could realistically claim it was for the tenant, and take the full deduction. This would give you a bigger tax break since repairs are not deductible for the owner portion.
Hope this helps!
Jonathan