I think your "1" boa will turn into 2, and then,,,,, LOL!
Boa constrictors are very unique, fun animals. I have 1, and wish i had another, but I opted for a coastal carpet female who's mother is 10 feet long and father is 8 feet.
My BC is actually a locality BCI (Barranquilla Colombia).
A really great starter boa is a BCI. They tend to grow the fastest and handled mistakes in husbandry and feeding a little better. Though if you are dedicated and willing to be patient and conservative, a BCC is fine.
BC's are decent sized animals and a female BCI from Colombia is going to be a 6-8 foot animal with some significant girth.
Once the weight of one of these passes the 20 pound mark, they are pretty large.
I know a few that have some hefty 8-9 foot Suriname BCC's that weigh a lot and they don't enjoy handling them as mush as a lighter boa.
If you have the time to check Amazon, look into buying THE COMPLETE BOA CONSTRICTOR By Vincent Russo. That book will tell you about everything you need to know about BC's. Also research anything and everything Gus Rentfro has written or posted about boa constrictors.
Check out Tom McCarthy's Big Boa Page. He has a ton of giant boa pics up. Some are really fat and out of shape, but he just complied the photos. He breeds some nice BCI morphs and has some beautiful Brazilian BCC's.
We have one royal python here, but to be honest, I find boa constrictors and carpet pythons much more interesting.
It sounds like you have breeding plans so maybe a nice BC would be a great shoulder pet for you while the royals do the breeding.
I'm not on here as much as I used to be, but I can assist getting you pointed in the right direction if needed.
This is my 5 foot 8 inch male Barranquilla, Colombian BCI doing his thing.
BC's are semi arboreal, and can be a real treat to watch in the right setup.