Search my posts, I've answered a lot of the lifestyle questions and pay issues. You're paid well enough to afford a normal middle class lifestyle with houses, cars, etc. You can live in base housing if you want to and can get it, which varies enormously depending on location. Every Doc I know lives out in town, except for the Southern California guys, about 50/50 there due to the insane housing prices. If you opt to live on base, you do not get your housing allowance.
As for deployments, in the Navy things are scheduled quite far in advance (at least for the long 6 month deployments). By that I mean 6-9 months out you know roughly when you're leaving, though schedules may change by a few weeks. The shorter underways on the ships can be short notice (72 hours is usually the minimum time), but are generally scheduled. The specialty trained Docs are working in the hospital, and will not deploy on short notice. The Docs at the Naval hospitals are on Fleet Surgical Teams, but these are huge and do not get moving at a moment's notice. You'll know well in advance.
The only very short notice call ups I've personally had were for short OPS (a few days). Some of these were "hey Doc, you're leaving tomorrow morning", but they are infrequent ( a couple in 3 years).