It’s important to realize that Guam’s Individual Wastewater Disposal System Regulations requires that you also set aside adequate space for a replacement absorption system (leaching field or trench) of the same size as required for initial construction.  This is to ensure that you are able to recover in the event of a failed septic system, which is always a difficult (and expensive) situation, but can be considerably worse if space is not available for replacement.  Your engineer or architect will take this into consideration when designing your home, along with other requirements such as parking and setbacks from property lines required under other Guam laws and regulations.
As long as your property meets the minimum lot size requirements and the soils are favorable for a septic system, there should be no problem fitting a reasonably sized home alongside the required septic system components and setbacks.