I definitely hear what you are saying as far as the rentals go. We've been using a rental agency that handles repairs, management, finding tenants, background checks, etc. It's pretty hands off.
We actually do the houses in one persons name based on some advice we received from a mortgage broker we had when we purchased our first home together (second home, but first married). At the time it was a way to separate the risk. If something happened it would only tank one persons credit instead of impacting both of us. It has worked out well for us, and is the only reason we can qualify for this third home.
I don't have a 401K currently. Our corporate structure is somewhat odd. The company I sold was an S corp with my partner and I as the two sole shareholders. We weren't employees, wages were sent to two sub corps (one owned by myself, and one by my partner). We do the same thing with our newer company. Because of this, I don't have a 401K through either of the parent corporations. I have my IRA and my taxable stock account with sharebuilder, and they offer a 401K plan for sole owners in a business (which my sub corp qualifies as), so that was my next move.
I have has a SEP suggested to me in the past, just haven't put in the research. I started my investing somewhat backwards placing almost all of my current stocks in taxable accounts. I'm starting to realize that while I should still invest there, I should probably do so AFTER maxing out my tax advantaged accounts.
Thank you for the book suggestion, I will definitely pick that up this weekend.
I think you summed it up, I just don't want to screw this up. I have watched my parents blow through all of their money as quickly as it came in, and as a result they likely are going to have nothing come "retirement" age. My first goal is to avoid their mistakes. College for the kids is definitely a concern. A 529 plan for that? I don't know about early retirement. I love what I do and see myself working in some capacity for a very long time, but freedom would be nice. Good short term and long term income coming in, so work isn't such a necessity.
You have some time, so educate yourself. it seems with the $5MM, you should be FI if you play your cards correctly.
It's difficult to make specific recommendations without details. For example, 529. Without knowing what state you live in and what you want to give your kids, it's difficult. some states offer crappy investments with high fees, but you may get a small tax deduction if you live there. But, you can invest in any state's plan, but you don't get tax deduction if you don't file there. so, it can make sense to pass on your state's plan for a state like Utah's.
My guess is, you can't do a solo 401k, but I'm not too savvy in this area.
Ask specific questions as they arise.