I doubt any shacks will be open they normally start to build them up at the beginning of November. Tourist season tends to start around then, coinciding with the first charter flights.
Have a lovely holiday

You do not say where you are going, in Baga a few shacks open early Big Banana and Xavier are among the first but I think that South Goa would be several weeks later

The place does look very sad and dirty after the monsoon also rooms and clothing can smell fusty until well aired but there will be plenty of dry days or even sunshine on wet days

The business and long term people start to come back in October (We are booked for the 8th) and place slowly comes back to life as thing get cleaned up or repainted. It is quite amazing to watch the change and the way it slowly happens, by the time you go home the better Restaurant and Bars will be starting to open ready for the tourist season in November

I would not bring waterproofs unless you already have a Packamac, you can buy a PVC jacket here for 200 Rs if you find you need it.

We were there from about the 20th and found few shacks open. We could use the Flying Dolphin(Calangute) as it has a permanent structure and is part of a hotel. Further down a couple more were open by the Calangute steps. Candolim was mostly closed at night though we did find a couple of places to eat at(Alexandras was great) and a couple of bars. It was very quiet but we did love it- but we were exhausted after a tour so happy to just relax. It did rain when we were there- our first day was the worst as little beach time would have spent. It rained a couple of other times but not for long.
Where are you going to be staying?

and there is some kind of life to the place

There certainly will NOT be any 'life' in South Goa then. Wat there first week in Nov' and was very quiet (apart from Colva but it's not very nice there).

Hi we went the 2nd week of October a few years ago.

It rained twice while we were there in 2 weeks, for about 2 hours at a time, but it was heavy rain.

Some shacks were open and most of the shops were open as well as all the restaurants.

It is much greener at that time of year.