In need of a good foundation

[Michael Slot]

Guys I need some help. I'm midway through house hacking my first duplex and I just discovered a wet spot in the basement after we got some rain. Upon closer inspection I found that I have a crack in my foundation that was previously patched and painted over. What do I do about this? My inspector and I didn't notice it when we walked through. Does this have to be fixed before it can sell? Should it? If so how does one fix such a thing?