A little problem here:
What I was thinking was Fnet is the weight times the acceleration.

It's not the weight times the acceleration but the mass times the acceleration.
Following this, the weight of 1 person will be 10 x 50 = 500 N.
Take your hint. Let X be the number of people.
The weight of X people will be 500X N.
Resultant force will be the tension minus the weight.
T  500X = ma
Tension is 1000 N, mass is 50X and acceleration is 2.
1000  500X = 50X(2)
1000  500X = 100X
1000 = 600X
X = 1000/600 = 1.67
Well... only one person can take this elevator to use its maximum acceleration it seems