I know my answers to your questions run counter to some others.....
I got one caique on impulse and did not plan to get another. More expense, way more noise etc. But my little girl, now 1 year old needs more attention than we seem to be able to give, even tho we both work from home. So I went on a search for a friend.
I was told a same sex bird would be the ticket but a breeder told me if I wanted them to share a cage do not get another girl. He said when they are hormonal they'll fight. So I went for a boy.
She is much happier now that she has someone to pick on. I mean, preen.
I still would have preferred to have the one but I think her happiness comes into play. She is happier with a bird friend. She tried to be friend with the Pi and the tiels but they are afraid of all that energy.
A few more thoughts....
I would never breed a WB with a BH because I don't like to 'muddy' the species. I will probably never breed anyway, I have plenty of time to decide but will treat it like my other birds that I also don't breed: don't give a nest, remove eggs, separate if necessary.
If you can only afford one that means only get one. Vet bills for one tiny illness or injury can set you back - and what if both birds were ill?
I don't know if this is your first bird but I don't recommend a caique as a first bird. Just speaking from my own experience, she's too hard-headed for a beginner - and I am not one, she still gives me a run for the money.