My understanding is that US forces get BAH (Basic Allowance Housing) if they chose not to live on base. If you live in base housing (MQs) then you don't get the allowance and your accommodation is effectively free. However, BAH will rent you a good house off base (e.g $1800 a month where I was for a Flt Lt - each rank and each area is a different rate). Many US servicemen seem to find somewhere much less than the BAH to rent and keep the difference. For married service couples, both get BAH, so can make a lot of money off this allowance.
I also believe that if you did buy privately and would lose a significant amount of money through posting if you sold (due to huge drops in property prices) then there was an arrangement put in place to compensate you/ buy your house off you - but this would require more research!
These allowances were on top of their basic pay, which appeared to be roughly equal to our own.
On the flip side, if they get posted to the UK for 3 years, they are not entitled to journeys home for the family, whilst we get a contribution (which normally covers the entire cost) towards 1 journey home per year per family member.
Also, on a 6-month det, whilst they do get R&R, they don't necessarily get shipped all the way back to the US.
This is by no means an exhaustive list, just some observation/ rumors I'd picked up.