Big difference is that most companies subsidize your costs as an employee or cover the cost entirely. You can look at MnSure's website to get an idea on what the cost will be for your family. If you are self employed (simply owning a couple rentals won't work) your health insurance will likely be deducted against your business income so that can help.
Another thing to consider is that you will likely experience a 1-2 month coverage gap that you may be able to cover by getting on COBRA. I ran into an issue here as my employer didn't send COBRA information out and MnSure messed things up so I went from January - March 1 without insurance. Not common on the COBRA part but just want to mention it.
Last if you are going self-employed make sure you talk to your tax person about the impact of self-employment taxes and your income projection. That is something outside of your question but it is very relevant in figuring out how much money you will have to make to match your wage.
Good Luck!