I would general recomend not doing it at all. If you want to keep males and females permanantly together then you should have a 1:2 ratio at least of males to female to eliminate problems of over breeding. Also if you want to keep mixed sexes i would keep them seperated until you know the sexes and let them get to breeding age before you put them together. Im not sure what you mean about not "inducing" them to breed, but leo's will breed when they feel like it, wether you want them to or not. If you keep a juvie male in with juvie females then he may breed with them when they are too young and your females could die.
This isn't to say that some people don't keep leos together, even on a 1:1 ratio without problems, but it is a formula not set up for the greatest sucess, especially if you dont haev enoughe zxperience with leo's to be able to tell early signs of trouble. An experienced leo keeper might have better luck because they may be better at acurately sexing, therefore seperating two males before there is a problem.They also may be better at recognizing symptoms of egg-binding or other such reproductive-based ailments and may be able to keep their leo's healthy through it all.
Im not trying to bash your idea at all, but this is my personal opinion. As far as how to get the leos, it really is up to you. At reptile shows and from proffesional breeders you can usually get a baby that they temped to be a certain sex, although this is not 100%, it is a pretty good chance that you can get the right combination. I would pick the leo's you want, grow them seperately, and put them together when they are at breeding age.
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0.1 Bearded dragon
0.1 mexican kingsnake
1.0.2 Leopard Gecko's
0.0.1 Rose Hair Tarantula
1.0 BTS
0.0.1 Reverse Okeetee Corn
0.1 Bullmastiff
4.1 Cats