We had a terrible experience with Oscar. We stayed for a total of six weeks as we were studying an English teaching course at a language school in Seville, and strongly recommend that you do not make the same mistake as us if you want to avoid being ripped off (Oscar twice tired to charge us hundreds of euros extra).
Because the primary reason for our stay was study, it was essential that we had access to WiFi. Oscar stated in the listing that the apartment had internet access, and so we didn't expect this to be a problem. However, after a few days at the apartment, the internet ran out. We immediately contacted Oscar to let him know, to which he responded that he uses a 'top up' system whereby he pre-pays for a very limited amount of data - as such, there is only sufficient data for a few days. He blamed us for over-using the internet (despite doing nothing more than using search engines for study purposes after we returned from school) before reluctantly agreeing to buy some more data. After a few days, the internet ran out again and we had a similar conversation with Oscar, who was equally as unhelpful as the first time. It became clear that Oscar was unwilling to provide internet, and we spent the majority of our six-week stay paying for access to the internet ourselves (by hot-spotting our laptops using our phones. This caused both significant expense and a lot of stress; as students, it made our stay incredibly difficult on a day-to-day basis.
While lack of internet was the biggest problem, there were lots of others too. Firstly, the single beds were extraordinarily uncomfortable; they were low-quality and poorly made, which meant they creaked really loudly every time you moved and made getting to sleep difficult |(the least comfortable bed I've ever slept on!). Secondly, there was about 90 seconds worth of hot water available before the shower ran cold. Thirdly, many items were broken when we arrived (including a chair, table, and the cable for the outside shutters in one of the bedrooms, which we had to fix ourselves).
Despite all of this, Oscar tried to charge us an extra 440 euros when we left - he claimed we had broken items (that, as explained, were already broken) and had left the apartment in such as state that it required an extra professional clean. Fortunately, we took a video of the apartment before we left that shows this was not the case (we were expecting Oscar to try and rip us off, as he had attempted to do so earlier in the stay.
In conclusion, I cannot urge you strongly enough to avoid staying with Oscar. The apartment is substandard, overpriced, and far from the city centre. There is extremely limited access to internet and other basic amenities, and above all, Oscar WILL try to take advantage of you and rip you off. Find ANYWHERE else!!