Mike, could not have said it any better, a PM can work and is designed to be way more effective than a single individual, just the systems and staffing alone will trump, you are so right your time is worth way more and no way you can be as diligent and efficient.

It involves engineering the sprinkler system to a specific design which involves CAD time etc.

I think this is mainly for interior design not structural issues.  

I've been a photographer for the past 12 years and do real estate photography and also have a background in design so I'm more than willing to help anyone in those areas if I can. 

Septic tanks are designed to last 50+ years depending how they are cared for (no grease and such) and without tree roots growing into the leeching field.

@William Allen  nice job... always great when the plan works as you design it.

Does anyone have recommendations for a good architect or designer to help with the plans?

I have an extensive background in mortgage banking and interior design.

Nice website by the way, did you do it yourself or hired a web designer?

Those funds should be parked somewhere safe and liquid, as they are not designed to make you money but protect you from financial disaster.