the tax breaks have expired, but Maine State Housing has some programs in place to assist with first time home buyers. They have the "gift of green" which will provide money to assist with closign costs and they also have a first time home buyer program. There are income limits for eligibility. their website is http://www.mainehousing.org/programs-services/homebuyer/home
Also for USDA/Rural Development loans, certain areas of Bangor and Orono are ineligible for RD loans, but pretty much anywhere else in Penobscot county will qualify. You don't say where your son is looking to purchase, but he can check availability on the USDA site. the link ishttp://eligibility.sc.egov.usda.gov/eligibility/welcomeAction.do
If I can be of assistance, let me know.. good luck to your son and his fiancee! it is a great time to buy a home!