In order to attract a larger population of bats it's a good idea as studies proved to build around 3 or 4 houses with different characteristics - like color or size - but if you pay special attention to a single one you can get a bigger number with it.
To build such a bat house is not a walk in the park so you either take your time to find bat box house plans of good quality or you can just use a professional that can build a custom bat house for you. The good part of this is that even if the cost are a little higher the custom design can be made especially for the bats in your particular region.
The design of these plans are getting pretty complex so we can talk now of a 4-5 chamber bat house but smaller ones good for a tight budget, and good for you experience are of course available. The best thing when you want to have multiple bat house but at lower price is to choose the smaller models. You can let your imagination lose and paint them the way you want it.
It's good to have lots of ideas when you get to building so you can take into consideration tips like: two small bat houses can be constructed back to back. To allow extra roosting space you can let some space between them. This aria however needs extra protection , achieved with the help of galvanized metal roof that covers both houses. Small houses may not be successfully in colder climates.
With all this in mind you can now decide to build a bat house yourself or just use the experts to do it with the specification you tell them.