My father is about to apply to be a permanent resident here in the USA.

Should he sell his house before he immigrates to avoid having to pay capital gains taxes?

If he is has started the application process is he liable for capital gains?

If he sells the house worth around 550k how how can we limit the taxes that have to be payed, for that matter are there any taxes that have to be payed on money he already has before becoming a permanent resident?

If the monies are in a UK bank and he wanted to transfer them to the USA would there be a way to put it into a retirement or savings account or investment of some sort again to limit any taxes to be payed?

Finally is there a way he could either purchase our/my house with the monies and then I pay him a loan payment back again to lower the taxable amount of funds or could he gift some of it to me (his son) or my wife again to lower the taxes that would need to be payed?

I need to keep as much of these funds as possible to pay for any medical expenses that may occur until he can buy into medicare in 5 years.

Thanks for any help given.
Kris