Pot/Container Size

[dlipford370]

So my friend just wants to grow some pretty small plants, it's his first time so he just wants to get the hang of it before he goes big scale at all. He was hoping to keep them in these 1 gallon containers for the life of the plant, The plants are almost a month old, but the roots are beginning to come out of the drain holes. Is this ok? Do those little roots just die off, but everything will be fine? I would appreciate your opinions, and examples of smaller pot sizes you used with positive results. Thanks.