I'd love to help with a projection date if you could provide more info's; i/e: zip code, square ft etc.
Best ROI on upgrade comes of course from general condition, but Kitchen and an entertainement area (bbq) will work and it's quite affordable.
After 15 yrs, I'm sorry to say........ you'll need to update restrooms, probably A/C and most surely the roof, which is one of the element Bank look at first to fund a loan.
I firmly believe that market will kick up in 2/3 years, or as soon they decide to apply the new property taxes laws.
Don't forget to trim trees and landscape, some paint wouldn't be bad idea either; if you brought it 15yrs ago and did not get tricked by latest mortgages traps, I would estimate you'll need about 10/15 k leaving you with plenty of equity.
If you need further assistance check the reference link and contact me.....I'm pretty sure I can solve it within 12 m;0nths!