A letter of intent for a new real estate project in Allston has been submitted to the Boston Redevelopment Authority by Waypoint Companies for 80 apartments at 61-83 Braintree Street. The letter of intent is for residential, rental, and retail space. The square footage of the land is approximately 21,824 square feet. The building size is approximately 93,000 square feet. The proposal also calls for 6,000 square feet of commercial space, as well as 68 parking spaces.