Using time series to predict house prices vs. multiple linear regression
I agree, the simple version of this problem isn't really a time series problem. There are some ways to deal with irregular intervals, but, houses are not all the same and we do not have a series of sale prices for it in most cases.

What may of course be very predictive is time. Housing prices probably have a long-term trend that's linear over the space of a few years, at least. There is probably a seasonality component, so month might be meaningful if used correctly.