HELP!! Can't find professional to advise on maximum building size

[Keagan Rubel]

First time building a MFR (8-12 units) and I need a professional to advise how many units is technically feasible to build on a small 100x125sqft lot in Pflugersville that is located outside of the city limits in the Extra Territorial Jurisdiction.  

I've reached out to a few architects in town but they all don't provide this type of work...

Any referrals would be greatly appreciated! 

Thanks.