Yep, if you have a septic system that is an absolute constraint on how many bedrooms a house can be listed as having, nothing else will matter. I'm regularly surprised at how many listings I see that claim more bedrooms that the septic is sized for, that is a legal liability for the seller and the listing agent. My current house lives like it has 4 to 5 bedrooms and we've used it as a four bedroom but it can only be listed as a three bedroom without an extremely expensive septic upgrade, so it is a three bedroom house with a couple of "offices", "playrooms", "bonus rooms", whatever.