The NRCS - Natural Resources Conservation Service - has a program in place to provide high tunnels, sometimes called hoop houses, to farmers to extend the growing season. Requirements are straightforward:
To receive assistance for high tunnels, applicants must be agricultural producers, producing at least $1,000 of agricultural product within the last year. Eligible producers must use commercially manufactured high tunnel kits; no electrical, heating, or mechanical ventilation systems can be added. NRCS can provide financial assistance to fund up to 1/20 of an acre or 2,178 square feet of high tunnel per farm where there is a documented resource concern. For 2011, financial assistance is available at a rate of $2.00 per square foot, $2.40 per square foot for historically underserved customers. Funds are also available for supporting practices associated with the use of high tunnels. Examples of supporting practices include, but are not limited to: diversions, critical area plantings, nutrient and pest management, and underground outlets.
Check out the program: find your local NRCS office using this locator and shoot them an email or make a phone call.
BeginningFarmers.org is another great resource to find grants, and check out this list of possible sources for grants and funding.