So here is the actual verbiage from Fannie Mae:Second Home Requirementsmust be occupied by the borrower for some portion of the yearis restricted to one-unit dwellingsmust be suitable for year-round occupancythe borrower must have exclusive control over the propertymust not be rental property or a timeshare arrangementcannot be subject to any agreements that give a management firm control over the occupancy of the1.

There's going to be some restrictions to this though. 

Most of the L-O restrictions only apply to consumer tenant/buyers. 

Restricted to Owner Occupied Homes. 

But we did look at purchasing a couple of units that were in HOA's that were restricted by an 80/20 rule.

Does the parcel of land have any Deed Restrictions on it?

Attorneys do disagree on the value of single purpose entities for each asset, but the SPE structure is often required by lenders, which may not be applicable in your case, because it restricts the business activities of the owning entity and can insulate the collateral from claims from other creditors. 

What are the loads in the house: electric baseboard heat; heat pumps; AC units; laundry; other motor loads.I am failing to see why you would need a 400 amp service without a proper load calculation.There is no code restricting the number of sub panels, they only have to have the correct install and protection.If I were in your shoes, I would connect with a licensed and insured electrician and ask for electrical audit. 

check with the lender and see what the lending restrictions are and then figure out whether you want to be active investor or passive can you find the right vehicle to invest the money if it's not restricted

HOAs and such may also have their own rules and restrictions.