This lot is located in a water recharge area and in these areas the towns are more restrictive on the # of bedrooms they allow. The town normally requires 10,000 square feet of land per bedroom (possibly more in a water recharge area), but if the town is part of an older subdivision than it may be grandfathered in and doesn't have to abide by these requirements. I do not have a solid answer for you but I will contact the listing agent and get back to you. If the listing agent does not have the answer than the town of Harwich health department is the next place that will provide an answer.
There are no restrictions on the number of bathrooms you can have. The town normally allows coverage of the lot which is no more than 15% of the lot size, which would be approximately 1500 square feet.
Let me know any other questions in the meantime. I will repost after I speak to the listing agent and/or health dept, unless you send me an email and in that case I will email you back with more info. Have a great night.
-Sunny Fellman, Realtor, SRES
Kinlin Grover Real Estate