Hello,
We are 3 adults travelling to Rome and Venice, for tourism in November. We will stay in Rome for3 nights and in venice for 1 night.
Please we need some advice for best accessible area to stay in both cities, bearing in mind we will be staying in budget priced hotels.
Any suggestions of cheapest transportation from Rome to Venice or vice versa? Should we first visit Rome or Venice if we are planing to go afterwards to Vienna?

Thanks in advance

Probably cheapest to travel by train IF you can buy your tickets soon. It is MUCH more expensive to buy tickets close to the day of travel.

Rome-Venice-Vienna if you plan to take the train to Vienna. If you plan to fly to Vienna, it doesn't matter.

Does "accessible" mean "close to the major attractions" or does it mean " an area where a person with physical limitations" can still get around?

A "budget-priced hotel" is likely to be in an area called "Termini" near the central station. Transportation to and from the major sites by bus, metro, or taxi is very easy from there. This area is not picturesque, so many Americans stay elsewhere, but there are many small hotels used by tour groups and European and Italian visitors. There is a supermarket (CONAD) and budget cafes and restaurants.

You are allowing very, very little time for two of the great cities in the world. Do you really need to go on to Vienna?

One night in Venice? That's almost sinful! Unless this is a well-thought decision, you'll regret it when you're there.
I also agree on Termini as the area to look for a reasonably priced hotel. At first impression it might look somewhat seedy, but it's an OK neighbourhood. Staying there very much reduces your logistics for getting to and from the hotel.
A long time ago I had an hotel near the Piazza San Marco in Venice. (I remember it having a lot of stairs and a very small room, so it must have been cheap.) For your short stay I would recommend something near the railway station (S. Lucia), for the same reason of logistics.
Please: try to get one more night in Venice!

What do you mean by "budget price", exactly how many euros per night?

If you give more info people can provide better advice.

Agree that , much as I love Venice, one night makes no sense if you are committed to moving right away to Vienna.

If it was me -- I'd either stay 2 or more nights in Venice, or skip it and travel directly from Rome to Vienna. With just one night you will get about half a day in Venice and then leave again the next morning.

Thanks a lot for your advice, I will try to find a suitable hotel in the area you suggested, probably I will try to extend my stay in Venice as you all advised.

Thanks again and regards.