For financial advisors who drop into cross border issues because of a single client, the best bet often is to turn to experts within the field who have more experience with expatriates.

"Sometimes I need to go to someone for advice who has a larger expatriate client base then I do," says Steinmetz.

One name that keeps recurring in conversations about cross border issues is Keats, Connelly & Associates Inc. in Phoenix. Bob Keats is the author of Border Guide, now in its seventh edition, which provides advice for those retiring to Canada.

"Because the United States and Canada share a close resemblance in social and cultural identities, Canadians tend to feel completely at home when visiting the U.S. Likewise, Americans feel the same when visiting Canada. Unfortunately, many of these visitors assume the laws governing investment, taxation and immigration are the same in both countries. They are not," Keats warns. "For anyone considering a move, the emphasis has to be on planning. The fixes we have had to make after the fact in some cases have been horrendous. If people just think ahead of time, they can avoid many problems and take advantage of many savings."

The types of investments people can make often change when they move outside the country.

"The United States is still one of the most inexpensive places to invest. Canada has a lot of expensive brokerage firms, and only 30% of investments in Canada brokerage firms can be foreign investments," Wruk says. "The rest have to be Canadian, which makes it more difficult to put together a well-diversified portfolio for your client. And Canada does not have the passive funds there that I am so fond of."

There are other issues to consider, such as the fact that debt incurred in the United States may immediately become due if the debtor moves out of the country. Likewise, transferring funds from an investment house to a bank can become a problem if the recipient is mentally incapacitated and cannot deposit a wire transfer in a bank, Wolf warns.

Health care and insurance can become an issue. Those moving to Canada will be covered by comprehensive Canadian insurance almost immediately. Wolf's client found her long-term health care insurance was not worth the expense once she moved to Mexico because long-term care there is inexpensive.

"What do you do if you die in another country?" asks Middleton. "Do you want to be buried there? You should know what the process is for getting the body back home. What happens to your inheritance if you die in a foreign country and your children are still in the United States?"

In a similar vein, "a trust moves to the place where the trustee lives," notes Wruk. "That may mean it will be taxed at the punishing Canadian tax rates. You may need a new will to replace one drawn in the United States. These are some of the things we have to advise clients to consider."

There are seemingly little details that can sometimes be the most upsetting to a client, Middleton warns.