Should I keep this long term tenant or not?

[Account Closed]

Hello my seasoned REIs:

I just purchase a property that has a long-term tenant (14 years) that her rent is well below the current fair market rent (25%+ less by its similar condition).

The unit is in deferred maintenance and needs many repairs and updates.

1) If I keep the tenant, I need to spend at least $5000 to just fix things to meet the basic living requirement. I can raise the rent and get even in about 6 months (if i can raise 25% but I doubt that's good strategy) but still the unit needs more care/update down the roads.

2) If I don't keep her and do a total remodeling, I'm looking at $20K. I can rent it for about 33% more and get even after 2 years.

The reason I'm thinking to keep the tenant is because she wants to move out in about two years later when her son graduates from college. And I feel bad to just ask her to leave now. At the same time, her rent is too below the market rent that I can't make even. 

First time posting question here, any idea/suggestion/opinion will be greatly appreciated!

P.S. Per my realtor who will help me managing the duplex temporarily, there is no rent control and no grandfather clause for long term tenant (still need confirmation from the city).