The best way to take a Bus from Sindhi Camp bus Stand Jaipur until Udaipur, Which would take 8 HRS approx. Fare would be around 600/- Per head for a AC bus and in Udaipur there are several Hostels I would suggest you to stay in.
Happy Journey and write back to me.
The best way to reach Udaipur from Jaipur is by local bus. You can also travel in a private cab. Check hotels in Udaipur here: https://www.tripoto.com/hotels