We'll be spending money on engineers, land attorneys and architects up front, so it's preferable that he get a cut of the overall deal in lieu of money up front.So, for all you developers out there, what are your thoughts?

You would have to double them up, or whatever a structural engineer / architect would recommend.

Seal with a slab is correct (some architects write in on the blueprints) they are looking for a 24' foundation to retrofit the bottom portion and also reframe the inside of the garage to withstand the 7.5 BIG QUAKE!!!

I'm also an architect in the area and could be helpful if needed.

I spent the last 3 months getting a 3 flat under contract using an FHA 203k loan, as well as doing a lot of problem solving and going back and forth with the HUD consultant, the Contractor and the Architect.

I would do some checking on the architect’s references that drafted the drawings.

Looking for anybody with an experienced architect. 

(As that can depend on the markets you're operating in)Also can an Agent help with Design of Home to make appealing to prospective buyer or Should I seek an Architect or Interior Designer?

If you have a good architect/engineer you can design modular homes with SIP Panel and if you work with the same contractor over and over again you can build an entire sub-division in a post-WWII fashion.

I've seen folks get 90% LTV on small apartment complex but it wasn't their first rodeo and they had relationships with the lender.Some things to consider is that you are responsible for a few more expenses than your standard SFH. you'll have to pay for attorney, CPA, landscaping, trash removal, and possibly pest control as well. if your considering owner financing any units off a apartment complex every unit must be individually metered.. that said you will more than likely have to do a condo conversion. can be expensive because you have to pay the county, a attorney, and  architect a lot of money to get it processed.your typically going to have higher repairs, maintenance, and vacancy with apartments because they are places that turn over more quickly compared to the desirability of a SFH. with that said the management side of have all 10 units in one place is amazing so when problems arise in different units your not driving all over the place to 10 different SFH.I hope this helps!