The phrasing in your question confuses me. Here are three possible answers:
If you have a conventional mortgage on a home built on 20 acres of land, then you can refinance assuming you have a good credit history, a stable income, and a debt-to-income ratio of 35% or less. Go to the Bills.com mortgage refinance savings center to get no-cost quotes from pre-screened lenders.
If you own the home outright and seek to mortgage the home on 20 acres, that is a possibility with a conventional loan as well. You also have the option of a USDA Section 502 loan if the property is in a rural area. See the U.S. Department of Agriculture Rural Development Web site for more information about Section 502 loans.
If the home is on Property A, and the 20 acres is an undeveloped Property B, and you want a mortgage on Property B, you need what is known as a "land loan." As I write these words in early 2010, the largest mortgage loan originators are not writing land loans. It is possible to get a land loan, but from smaller loan originators. Land loans are typically five years in length, and are designed for people who seek to develop land.
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