Primary question to check on with your local zoning group, are they allowed. Same goes for individual collapsible storage units. The following discussion is just on Cargo Containers.

Only if you have cheap/extra land and can do rock roads (if you have to have concrete/asphalt roads, you need a higher return unit).
If your in the country and your zoning allows it, go with 20 foot Cargo containers as a good part of your mix. Put some gravel down at the front and back of the unit to get it off the ground. If two rows, put them back to back. Buy in groups of two. They can be delivered two at a time on a tilt bed truck trailer. Delivery cost will be the same for 1 versus 2, about $120 within 30 miles. Tell them ahead of time how you want them to face when they are unloaded. They will not get placed perfectly so plan to unload then 20 to 30 feet away and have a crane truck set them in place. I would recommend buying about 20 at a time, to make it worth everyone's time.

Depending on how close you are to shipping areas, your container delivered may run $2,100. Rent for $50/month.

A 10 x 15 or 20 traditional outside access unit will run $3,100 installed. 10 x 20 same market rents for $65/month.

Containers are only good for clients who can open/close them. Appreciate their airtightness.

They will rent for less. Example: 8 x 20 ft container $50; 10 x 15 traditional $55; 10 x 20 traditional $65 in the countryside.

No property taxes since they are not attached to the ground.

You can buy as you need them.

Have to many, just sale them.

Talk with your tax person. Should be able to write them off in year one.

Recommend you use silver trailer roof paint. This lowers the inside temperature significantly. Also paint the Visual exterior sides a consistent light color to reflect the sun. Sand down roof and side rust spots first, then prime. We have 40 of them and they look great painted one color. Everyone wants to buy one.

When you buy, pick no leaks in roof or floor. Side dents are okay. Easy to open doors. Don't buy single trip containers they cost to much. Also don't plan to fix them up. If you replace one of the plywood floor panels with original material it will be about $800 per 4 x 8 sheet. Door hinges and bars will be costly to replace.

For Property insurance these are treated as Personal Property and not as buildings. Make sure you have enough coverage under Personal Property, along with your lawn mower, office equipment, etc.

Recap:

- Cheaper than traditional

- rents less $50 vs $65 but more profit

- no property tax, since not attached to the ground

- Can add and sell as needed.

- Insure as Personal property and not Property.

- Bank may not want to loan against, since moveable.

- Harder to open, so not good for some clients, others like them because the are more secure and for pest control.

Separate topic. The units below were 2 foot under water, over the roofs for a month. One year ago. Floors, metal and door hinges are fine. Very durable product. Not a product for every location, but works well where possible. Would go good with a Boat/RV/Vehicle storage location for onsite storage.