With 1 male and 3 females you wont even notice they have given birth unless you catch them at the right time, In a tank that small any fry will quickly become fish food and any that don't you can give to other people wanting to start, Or get adventurous and grow them on.

unfortunately most fish stores seem to run on the " if you say it with confidence the customer will believe you" quote.

I'm sorry but my opinion sides with the bigger the tank the better for the beginner. you should be doing a lot of water changed for that many fish in that small of a tank. I really wouldn't be happy with putting any fish in that size except fry.

Of course it can be done, and that's only my opinion