Most people like me can only be contented with getting an apartment in a metropolitan city. So, I would just share my own way of avoiding 'problematic' unit. By 'problematic' I mean 'haunted'.
It is best that you can bring a compass to visit the premise of your choice but this is not always possible not to mention that such a method is clumsy.
Once I audited two adjacent apartment units in a row. The first one showed that the house was facing south. When I audited the second unit, the compass needle took an about turn and showed the direction as north. So, the second unit is definitely problematic.
So said, to many others; bringing out a compass maybe embarrassing. The next tell tale sign is to look along the common corridor. If most of the apartment units has some kind of earth god or heaven god templates or the like, then it is likely that some spirits maybe present.
Then you should pay much attention to the ventilation in the corridor and later inside the apartment. If you notice some musty scent, that means the air is not circulating enough. As per rule of thumb, still air accumulates spirits.
It is best to avoid such an apartment unless you want to invest in a new ventilation system.
Other than that, if you are accompanied by an real estate agent, then see if he/she is doing anything funny. For example: knocking on the door and pressing the door bell. If your agent did any sort of actions as described, then be wary of the unit please.
Before you enter the room, first please just step just one foot in and one foot outside the brim of the main door. Then close your eyes and notice any emotions you might have: happy, sad or just neutral.
After that, please pull a chair and sit in the middle of the living room and notice your feeling. Since we spent much of our time sitting in chairs, it is worthwhile just to invest a few minutes to sit down and that will make you feel the environment much clearer.
Avoid an apartment that is too near a big tree. If the view of tree top can be seen from the apartment or if huge tree roots have extended towards the front door, then the unit is likely to be haunted. Not to mention that fallen tree branches can be a safety hazard during rainy days.
Many parents like to bring their babies when choosing a new apartment. My advice is that we must avoid using our babies as guinea pigs. While it is true that babies are very sensitive to the presence of spirits, they are easily scared. When those babies really see ghost, they will feel frighten and cry out loud.
Since babies have weaker souls, they are easy prays to those earth bound spirits in the apartment or its surrounding. If babies suffered spiritual attack and the parents are not aware, the baby may be possessed by spirits that might deter the babies' mental development.
The best time to visit an apartment is early in the morning and in the evening. These are the best timing to give you an idea on what you are investing.