I can tell you the Cons right now, and it all boils down to one main issue: they are non-standard types of building.
1) Permitting at the local level. You have to get the city/municipality to sign off on everything, and their codes and regs likely won't be updated for your project. You may be the one who gets to force them to update their codes and regs, assuming they agree to let you do it. This will be costly and time-consuming. So... kudos to you for being a pioneer, but keep in mind pioneering is difficult and costs more than following the trail that others have already blazed.
2) Renting. Tenants generally have amenities and features they like. While shipping containers theoretically are just as good (if not better) structurally, they just don't "look" normal. So you might find a very small niche market of people who like living in what resembles a ginormous corrugated boxes stacked on top of each other, but 90% of your renter pool isn't look for that, no matter what trendy color you paint it.
3) Construction and Maintenance. Finding labor to work on it will again require someone who is a specialist in those kinds of buildings. Odds are you will pay a premium and wait longer. There will also likely be construction issues such as not being able to run wires and plumbing through walls, unless you frame out the interior with drywall. Also, shipping containers are odd sizes: 8 x 40 and 8 x 20 means rooms can only be a certain size unless you want to tack expensive modifications.
4) Financing. These units are not going to qualify for anything other than short-term, commercial financing from traditional lenders like banks. Ultimately, you'll probably need to pool private investor funds. Rates will likely be higher and subject to market adjustment after a few years.
On the bright side, you'll have units that can withstand hurricane force winds and that get taxed as personal property rather than real estate, and also depreciation might be on a shorter timeline. Not sure about that last one.
A standard shipping contain cost in my town is $3500 for a "one trip" 8 x 20. $4800 for 8 x 40. But that's just the box. Costs will vary depending on how easy it is for your supplier to deliver to you. My town is right on a major rail line, so we get them in frequently and they can be picked up with semi-trailers and delivered easily. After acquiring the boxes, you have to heavily modify them so people can actually live in them. You may also have to install them on commercial land that has been approved for residential structures. This will increase the cost over a standard residential multi-family parcel.
I would say for even an advanced investor, it would be a highly ambitious project with many unforeseen, expensive pitfalls. Works your numbers, then double them just to be sure.
