Find accommodation in Huelva is quite easy, and more than 90% of international students get a room in 1-3 days, so don´t worry about it.
To rent a room or a flat, I reccommend you to go to the International Office and ask to the people of ESN Huelva, they will give you a list with a lot of flats or rooms available, and they even will call to the owners if you can´t speak Spanish, so it will be easier. Note that all ESN Staff are all volunteers, so they are not going to charge you any money for it.
Another issue about accommodation is, what to do the first night or if Im going to Huelva during the weekend??.
Well, the best option is to book a hostel / hotel for 2 nights.
The cheapest options that you can find are: Hostal Calvo, nothing special but right in the city center, really cheap and clean enough to live, Albergue Inturjoven, with breakfast included and really good services, Hotel Marina, close to the campus El Carmen but a little bit more expensive, or Hotel Costa de la Luz, also with breakfast included.
You can check prices and availability clicking in the links.