As I was working on their taxes, I noticed that cost segregation was based on $180k worth of renovations while the total rehab cost was $310k.

Too few details to answer (Of course this varies county by county, all questions could be answered by reading the (zoning)/building code and/or clarified with a visit to the county planning office).but some clarifications because: lots of things are "tiny homes" but what you describe small houses "on permanent foundations" needs to be clarified , tiny homes could be:-stick built, see below. check your county code/planning dept-stick built cabins/recreational, a specific zoning and potential occupancy/etc restrictions but worth looking into where the zoning allows for it -hud manufactured homes (smaller singlewide perhaps 400sq ft 600sq ft minimum)-non-hud park models (on axles), ansi standards- other "RV's" built on a chassis:  organizations, state agencies, etc - will certify factory built (or sometimes inspected professional built) tiny homes on chassis - to whatever standards ansi, riva, dot/ l&i?

Yep, we have some of our folks handle inbound calls as well, needs to be a large amount if you want to make it worth it. 

I agree it would not be worth it.  

Unfortunately it can be difficult to identify legitimate offerings both on the lending and wholesaling side but if you stick to larger more reputable groups you should be in good shape.As far as requirements, hard money / private money lenders will typically require you to put at least 10% down on the purchase, often more.

Note that you typically have two years from the date you paid the tax or three years from the date you filed the original return (whichever is later) to submit an amended return.FORM 3115This is a specialized IRS form that is used to request permission to change an accounting method.

Even at a full listing price it was still worth 50-75k more!

DSCR loans are typically not reported to credit agencies. 

Single family in general in DFW area I typically see about 30-40 down will break even or cash flow.2. 

As @Jacob Sherman mentioned, lenders prefer and typically require to be the sole debt on a project (mortgage).