If you do not have a choice, you can get away with using electronic app compass or real life compass and the silk string, to properly determine both ~ the front door and property's facing  direction. Or though it is always best to use authentic Luo Pan for accuracy, it is ok to use hand on tools, if you can not afford one. 

One of the easiest easy to determine room door direction, for example, as well as opening direction flow, by putting regular compass on mobile compass app in the middle of the room, on the floor or clear non-metal surface, and, attaching the silk string to it.

You can tie the string to the door knob and other end to the compass. This will show you an exact degree and directions you need.

FengShui Compass by First Bird Technology cost $1.99 and you can download it on Google Apps.

Buy Authentic Luo Pan HERE or HERE.

Some other accurate good mobile apps: Navigation for lucky travel by Mingli.ru.