Assume home is in a very strong location and assume we would do a high quality renovation and use an excellent architect and builder who's work I know and trust.

 :)But as a starter, here's what I would do:Draft a master plan (and try to stick to it)Talk to architect ASAP to work on your plan of additions.Budgeting: bring in at least 3 contractors to interview and bid on your project.  

The reason is that I re-sided and changed the entire color palette, and the light brown shingles that were there looked dated and were the entirely wrong color.I considered both painting them, and replacing with either standing-seam metal or new architectural shingles, but the architect actually suggested that we wanted to minimize the roof, visually.I've been very happy with the results.  

I to am a registered architect by trade and I've seen some very damaged slabs here in Houston that would require 20k+ to repair and some that would just require 4k for pressed piers in the corner of the foundation.  

They are the ones that architects look at when we think about or talk prefab.http://methodhomes.net/https://www.bluhomes.com/homes-landingYou might also want to look into doing a custom built home.

They usually place the architect's rendering and the floor plan on there to generate interest.

We have decided on our plan, just waiting on an architect to draw this up.   2 of the bedrooms have a coat closet as well as the regular closet(I guess because it was built in the 20's) so we decided to take the coat closet from middle bedroom and a little of normal closet in back bedroom to add extra space in our only bathroom.  

Is it my architect who draws up the plans and subs out the plans for electrical / plumbing etc?

This would require Architects and possibly some entitlement work.2) is to go through any other entitlements.  

I'm going to hold off on posting all the numbers until it's sold -- you never know when one of your buyers might be trying to dig up information on the Internet to help them get negotiating leverage...But, the rehab costs -- including architect, engineering and permits -- were around $230K on this one (basically, everything other than purchase costs and holding costs).