23 year old guy looking for a accommodation in Praha

Hello, my name is Eder, I'm Brazilian and I want to rent a room.
 I would like to explain the situation. I am going to study at Czech University of Life Sciences and I need to apply for a visa/residence permit. I only have 3 more days of visa in the European Union and one of the documents to apply for this is Proof of Accommodation. I was going to get my Proof of Accommodation from a friend of mine, but I can't stay in his house anymore, and now I'm looking for places to rent.

I can't receive Poof of Accommodation after going to see the place, because I need to have a visa in hand to be able to check-in. So, I prefer to believe that it is a good place to live in.

Similarly, I need to sign the contract and pay the deposit (if you have it), but I prefer to do everything from here (Lviv), and them go to Praha just to live.
 I really don't want to cheat on you or break the law, I just want to live there and unfortunately, that's the paperwork I have to do.

Could you please give me an answer and we can reach an agreement.

Thank you very much in advance.