How much does he make?
What does he do? Is there anything he'd love doing that could still pull in -any- money? Part time?
How do you feel about your own job? Could he assist you in doing it? Do you feel good about working -your- job till 65 or whenever?
Yes, you could do it, but that's barring any negative changes in the situation(such as you becoming unable to work) at which point, you'd have enough money to last some time, but then he's been out of the job for "x" amount of years, where "x" adds a non-insignificant burden to attaining a job.
Consider alternatives as well. What requires you to live on 2400$ a month?
Considering it's 5 years out(ish), it's not a terrible plan, but it's not the best, most fully developed one either. Also, maintaining 50k in actual cash is probably a bad idea. Instead think about bond/stock allocation, and a slow rotation/feeder pipeline of bonds/CD's if you want to know you have money available, without completely wasting the ability of 50k.
Also, assuming 7% investment growths per year, investing 30k a year(at 2500$ a month) turns into 180k in 5 years, not 150k.