Light stocking of african cichlids

Hello,
I'm fairly new to aquariums and have never kept african cichlids. I
bought a 75g tank from the lfs about 2 years back and kept some community
fish in it for awhile. Due to a really busy schedule I didn't have much
time to take care of them and some of them died. Most others I gave away to
my grandmother who gladly took them and is still taking care of them. Well
anyway, the tank is a 75g with 2 penguin bio-wheel filters, and I made a
custom styrofoam/concrete background for it. So the cichlids can have a
more natural environment, although this took about half of the space of the
tank.

The question: Can I stock it lightly, 3-5 fish instead of overstocking it?
I'm running low on funds and I don't want to spend a ton of money all at
once. I can buy everything I need to take care of the fish, but the fish
themselves are very expensive. 8+ dollars a fish. That can lead to alot of
money. My plan is to buy some yellow labs, and maybe a trio of
Pseudotropheus demasoni, if these fish will go good together, and then bread
them. The fry I was later going to raise a bit and then trade off to the
lfs for some more fish. (Maybe) Will this work? Can I get a trio of yellow
labs and a trio of Pseudotropheus demasoni? Will that lead to lots of
aggression? The fake rock has lots of caves.

Thanks,
Chris