The answer to this question is going to entirely depend on the town you’re located in. The zoning ordinance should be available to you (either online or by requesting a copy from the town). It should have instructions on what you need to do.

The state also has a permit navigator https://dec.vermont.gov/permitnavigator which can be helpful in determining any state level permissions you might need.

It seems like it should be relatively straight forward. but you might have to ask them (the town) what you need to confirm. Some towns are pickier than others for sure. We needed a curb cut permit (there were specifics on like how big the culvert had to be and how wide the driveway had to be at the street), and a permit for the house. I think that was it. The WW permit you already have. The well is already there. Is the barn worth saving? When I think VT barn... I think pretty basic, maybe not great foundation, etc.

Just go talk to the zoning admin.

The only thing that I would see as a concern is how you intend to manage waste until the septic system is installed? True composting toilets are fine and permitted when managed properly, but a pit style outhouse is probably not going to be ok unless it's a sealed vault style.

My neighbors did the same kind of thing (slowly built over 3 years while living on the property) were going to need to a special permit for their toilet and would need to bring the waste to the landfill because they couldn't safely dispose onsite; they ended up renting a porta-potty until they had their septic system in.

Obviously you don't want to contaminate your land and water source. Personally, I would prioritize septic installation above most all else, most people I know who have built or intensely rehabbed focused on that early on, well before contruction/rehab/plumbing.

Go talk in person. You can better describe what you are doing and they can give you the appropriate guidance.

My approach has been, get permit, do work. The town can fuck right off once the permit is issued.

Every town is different.

Some have no zoning, some require a permit to install a mailbox. You won't know until you go in and talk to someone. Or post the town and someone here may have experience

Other considerations-

1. Whether the town enforces International Building Code and inspects your work.
2. Whether the town enforces International Fire Code - fire safety regulations.
3. Driveway access and regulations.
4. State regs are not handled through the town.

The zoning is the easy part. Complying with building and fire code (IF THEY ENFORCE) is where it gets pricey.

Be ready to learn.

Yelling at town employees will only slow your process.

Regardless of the town I wouldn’t tell anyone you are building an outhouse. Rent a port-a-john until you have a septic put in.

Yeah guess that's the right answer. I just get nervous when I need something from a civil authority.

Hey that's a great link thanks

Most town clerks are easy yo talk to, just give a call. The zoning administrator would give you the info you need bit the clerk should get you started.

As long as you aren't cocky or combative, you should be fine. Tell them what you want to do and ask if that would allowed.

Going to depend on your town. I know our Development Review Board scoffed at burn/composting toilet and length of time as "primitive camp" for a neighbor who was doing basically the same thing except building an entire new structure. Their opinion was the person would likely always live in the primitive camp. The neighbor eventually gave up and sold out.

I would probably ask about phase two and see where that takes you before breaching the composting toilet/primitive camp. I would see about the renting a portolet option cause you can just say that is for the workers for construction.