Where should I look for summer job at Brighton for a EU student?

Forget about it in 2020, I don't think it would be very safe, or even possible. 

Do you mind dancing naked?

Because nobody is really looking for a one month employee.

Brighton's a great place for casual jobs. Definitely cafe/bar work and hotel workers are always in short supply. However do bear in mind that there's a huge event coming up for UK, namely Brexit, and at the moment no-one has the foggiest idea what's going to happen with regulations for what will then be foreign casual workers after March of next year when we leave. So be prepared to have to fill out extra paperwork to enable you to be able to do this. But is it possible, definitely!

As far as accommodation is concerned, just do a trawl online. It's the best way to get a choice within the budget you need.

Brighton is a great town to visit. It's cosmopolitan, friendly to all people and fun. Enjoy it!

Try hotels.

Unlikely and depending on Brexit as the UK will have left the EU then and any temp jobs will already be taken by students there at that time, you will have difficulty finding anywhere to live as it will be holiday time and holiday makers will have already booked, as will youth hostels

Bars, Restaurants are your best bet. I doubt if visas will be required by next summer

Forget it, even if we not out of the EU no one will employ you for such a short time. Seasonable jobs are for 3 months or more.

You will need a visa by then as we will be out of the EU

By the time next summer comes, the UK will no longer be in the EU - you may not be permitted to work here without a suitable visa. It's unlikely an employer would go to the legal trouble and expense of employing a foreigner for a few months when there will be plenty of British students also looking for summer jobs.