Brian,
There will be a lot of due diligence, and consideration in this type of project. Plenty of ways to "leak" funds during acquisition and construction. Let alone when the real work begins as you put together your business systems to fill and keep filled those units. If you are investing your own funds then caveat emptor!
But if you are being trusted by an investor then ... it's even more important.
Consider putting the time in a workshop or two on the subject. Do the homework indicated to create a business plan. Plan out every cost you possibly can. Check with existing owners/investors on best practices they've found (be specific as possible please if you have questions). Tour existing sites. Consider a partnership/mentorship with a current investor. Flesh out two or three back up plans if things fall through at various stages.
This is the work required in these deals. No shortcuts or secret formula. Gotta do the work.
Stepping into a construction project such as this could have very heavy negative consequences, and isn't taken lightly. If this involves "other peoples money", you owe it to your investors and underwriters to take the time and develop your skills before putting funds at risk.
I know Scott Meyers workshops appear to have a lot of this type of information (though I haven't been to any myself) and if you're considering going the route of self storage I would recommend seeking these types of resources out before any extremely costly mistakes.