The time to solve estate planning problems is before they happen. Otherwise, what you think is a loving act—leaving your home to your heirs—can turn into a financial and familial disaster.

Estate planning is complicated, and you’ll need help from qualified pros, but here are four reasons why you should start thinking about an estate plan now.

1. A good estate plan can keep your heirs from fighting

Say you intend to leave your house jointly to a son and daughter. But what if, as often happens, one child wants to live in the house and the other wants to sell it? A reasonable estate plan would not force one child to indefinitely forgo his or her share of the value of the house.

Possible solutions:

• If you have other assets, it may make more sense to divide your estate, leaving the house to the child who wants it, and property of equivalent value to the other.

• If the house makes up the bulk of the estate, an insurance professional can talk to you about a policy that would provide enough money for one sibling to buy out the other’s share.

• In either event, talk with your heirs up front so you can structure your estate plan to head off potential problems.

2. A good estate plan means no financial surprises

Consider these two scenarios:

• You’ve sold the family home and bought a retirement condo, with a mortgage. Your heirs will eventually inherit both the condo and the loan as part of the estate. But they can’t assume the mortgage unless they’re planning to live in the condo. They’ll have to pay it off. That can be a nasty shock, explains A. Raymond Benton, a certified financial planner in Denver.

• It’s very possible that in later years you’ll want a reverse mortgage to help pay for nursing care, for example, while you stay in your home. Upon inheriting the house, your heirs will have to come up with the money for the outstanding loan. Otherwise they’ll likely have to sell the house to pay back the lender. The bank will not allow your heirs to just assume a reverse mortgage.

Explain your situation to your heirs in advance as part of your estate plan, so they can be financially and emotionally prepared to accept an encumbered house as part of the estate.

3. A good estate plan means less of an estate tax hit

When it comes to estate planning, the biggest issue to consider is taxation. It’s a particularly thorny problem right now because the federal estate tax is in flux. If you die in 2010, there’s no estate tax, but it will almost certainly come back in 2011.

While that sounds like a good thing for 2010, there’s a catch: There’s only a limited “step up” for home value in 2010, according to Robert Demmett and Gerald Marsden, CPAs at Eisner & Lubin LLP in New York. When there is no step-up, your heirs could end up paying capital gains taxes on the difference between what you bought the house for 30 or more years ago and what they get for it when they sell. With a full step up, they would only have to pay tax on the difference between what the house was worth at your death and the sale price.

There are strategies for dealing with this, now and in the future. An estate planning attorney can set up a trust to help manage step-up issues.

4. A good estate plan can keep you from losing your house if you get sick

Of course, you may be thinking, “This is all academic. I’ll have to sell my home to pay for eldercare.” However, with a combination of long-term-care policies and trust-based solutions, you may be able to take care of yourself and leave your home to your heirs. Consult a lawyer experienced with estate planning or a qualified financial planner.

Richard J. Koreto is HouseLogic’s managing editor of finance, taxes, and insurance. He has been editor of several professional financial magazines and is the author of “Run It Like a Business,” a practice management book for financial planners. He and his wife own a pre-Civil War house in Rockland County, N.Y.