Well, it's best to quarantine them separately in individual cages unless they came from the same place--vet check or no, some dangerous and contagious diseases may take as long as 10 months to incubate. Strict attention to hygiene to prevent any transfer between enclosures can minimize risks. If you're running a rescue, you know you may get in animals from a variety of questionable backgrounds--you don't want to rescue a snake only to have it die of IBD or paramyxovirus brought in by another snake (and that's just the tip of the iceberg--vet checks don't cover things that are not yet symptomatic).

While you might get away with housing 2 females together if completely necessary, housing 2 males together is likely to lead to some knock-down drag-outs.

YouTube - Ball Python Combat

You wouldn't think they had it in them, but there you go.

As folks have stated, if it's not your intention to breed, house them separately, and the female may not lay a clutch. They don't always, even if they lock up multiple times.

A Hovabator is a decent choice for an incubator, though I would recommend purchasing a better thermostat and not using the wafer thermostat it comes with. Incubate at 88 or 89, and use a 50/50 mix of vermiculite and water by weight, for the media. (Other methods exist, but this one is easy and proven).

The female may try to take your hand off when you go to remove her from the eggs, so put a hand-towel over her head, and gently unwind her. Wash her in a weak chlorhex or very dilute detergent solution, and wash and disinfect her cage and all cage furniture after you remove the eggs. This will remove the scent of the clutch, and she should begin feeding again after a few days' rest.