My first constrictor was a normal ball python, I quickly purchased a female Colombian BCI, then a EBV RG hypo pastel male, and just recently an Anery female BCI and a hypo male BCI.
So no you can have just one.
0.1.0 Normal Ball Python
0.1.0 Colombian B.C.I. 2013
1.0.0 EBV Red Group Pastel Hypo Jungle B.C.I. 2013
1.0.0 Hypo Colombian B.C.I 2011
0.1.0 Anery Colombian B.C.I 2010