Sounds about right. It is very hard to get the average down because a lot of things come in large-price "units" such as bathtub, window, door, HVAC, water heater, range, refrigerator, and these are in disrepair a certain percentage of the time. One person can paint maybe two rooms per day, and everything prior to painting takes time too. If the floor is soft, you'll have to repair that. By the time you're finished, you could be into it for $10k or more. However, a new home costs about $40k all-in (maybe you can get a little cheaper, but not much after installation &c). So there is a big delta between [new home @ $40k] and [used home @ $20k (includes some profit for you or maybe you budget $5k for purchase & $5k moving/installing).
The "homes" side of the business is the dirty little secret that no-one talks about. It is very expensive to fill your park if your residents aren't going to do it for you (by coming in fully financed with their own home, for example).
Whether you run a rental model or a sales model, people want to pay over time and you are out all the cash up front. That's a tough business, especially if you don't have a good "pump" and a good "filter."