Go online and find a few good layouts/ideas you like and take it to a designer/architect/engineer and let them take it from there.

But all of the points you lay out about real estate investing boil down to the averages.  

Convenient enough but a house with the exact same layout but without the finished space above the garage just went under contract for 188k and the finish is less than what this one will have.  

To determine the value of a mobile home you must understand the market, the type/size/layout and the condition.  

An alternative thing to consider, if you both have strong incomes, you may want to determine if your borrowing ability (number of mortgages) would be greater if you purchased, and mortgages, properties individually (some in your name, some in your wife's name).Since you are thinking about this all upfront, this would be a good time to sit down with your wife and lay out a roadmap of your near, mid, and long term real estate goals and then meet with an accountant and attorney who specialize in real estate to determine what ownership structure best fits your initial needs and how/when you would move towards more structured (i.e. corporations or trusts) ownership and how to minimize your tax situation in the process.As part of your self-education, I would recommend picking up a copy of Steven Cohen and George Dube's "Legal, Tax and Accounting Strategies for the Canadian Real Estate Investor" It will be a good primer on the subject. 

that has at least 3bed/1.5bath layout post-1978, this is due to the lead paint I don't want to deal with.  

Upgrades to all kitchens, bathrooms, refinish hardwood floors, potentially replace roof and potentially change layout of living/ kitchen into open concept.thanks,satha

Outdated layout-- this can be a big issue for rentability and resale value if the layout is jacked up and not easily fixable, especially not enough bathrooms (1 bathroom for 3 or even 4 bedrooms used to be common but nobody is going to want that now, new construction often has one per bedroom).

I lay out the pros and cons of each scenario and let them decide.  

I've seen projects on HGTV of MFR using shipping containers, and they had a great layout and look.