Don't know much about a program for estimates, but Quickbooks will do estimates, however it might be to complicated. 

http://www.fourlane.com/quickbooks-training-estimates-sales-orders-and-invoices/

For a laptop I recommend something with an Intel i3 processor (6th generation) with a minimum of 4 gigs of ram, and I would get a 15.6 inch display to make it easier to read. Staples has a Lenovo that would work for $260.  There might be some more deals later for Memorial weekend.

 http://www.staples.com/Lenovo-Ideapad-300-15-6-4-GB-RAM-500-GB-Hard-Drive-Intel-Core-i3-6100U-Processor-Windows-10-Laptop/product_2126772?cm_cat=358129&cm_ite=Ongoing+-+Staples+Basic&cm_ven=CJ&PID=361116&cm_mmc=CJ-_-361116-_-361116-_-10422268&SID=ebs2d0d4986d1464176987681sbe&cm_pla=361116&AID=10422268&storeId=10001&CID=AFF%3A361116%3A361116%3A10422268&CJPIXEL=CJPIXEL