Your first priority should be location. Try to find an area that has plenty of demand. You should also consider what resale opportunities you are likely to have, already when purchasing. Moreover, get acquainted with the housing company: its size, its financial standing, and so on. Big, well-kept housing companies are usually a safe bet for an investor. The condition of the apartment is also of relevance: your rent can be set higher and your tenant is likely to stay longer. If you find a potential property far away from where you are located, consider how to manage all aspects related to the lease.
When you are selling your investment property, basically the same rules apply as in selling your own apartment. In residential property investment, selling should also be well thought out. If you change your investment strategy, selling might be a smart option. Other possible outcomes include situations where the apartment does not make you the profit you had planned for, the desire to cash out on the increase in value and use the profits to invest in something else, or swapping an older apartment to a pristine property. So, as you sell your investment property, be systematic and follow your strategy.