Look at the supply and demand fundamentals of the market, what is driving those, and if those things are durable or not. In the simplest form, you can look at long term historical pricing to see if/how long/how steady the history of price and rent appreciation is ... there WILL be some fluctuation as RE is somewhat cyclical and nothing ever goes up in a straight line always, but does the neighborhood and surrounding neighborhoods have a long term track record, spanning several up/down cycles of appreciation and rent increase?
What is driving supply? How easy would it be for a developer to come in and build a bunch of housing to meet increased demand? Are there lots of vacant, buildable lots in or around the neighborhood? How easy does the city make it to build? Are there natural or unnatural boundaries that limit growth? Oceans, mountains, rivers, lakes, national forest, etc?
For demand, what is the average income and earning power (education level, etc.) of the residence? Are new jobs being created? At what rate are people moving there and is that persistent and sustainable? Is the employer base diverse or concentrated in one employer or industry? What sort of jobs are there? Blue collar? White collar? Is there a top notch university nearby? Steady, well paid government jobs? How many and what types of small business start ups are there. Are there boarded up and vacant houses? Blight? If so, do they stay boarded up and vacant or get snatched up as quickly as they hit the market, remodeled, and filled?
Other supply and demand metrics to watch the value and trend ... population growth, unemployment rate, vacancy rate, affordability, etc.
I think of things in terms of a "quad chart" ... on one axis you have demand: Low and High. On the other axis you have supply: limited and ample. The quadrants are:
I - Low Demand, Limited Supply & III - High Demand, Ample supply: Prices and rents will tend to keep up with inflation. Mid to low initial cash flow that is steady over time.
II - Low Demand, Ample Supply: Prices and rents will tend to NOT keep up with inflation. High initial cash flow that decreases over time.
IV - High Demand, Limited Supply: Prices and rents will tend to exceed inflation. Low to negative initial cash flow that increases over time.