If I had a large amount of money and didn't need immediate cash flow I would be interested in what Joel Owens says, NNN properties or apartment buildings. If you don't need the cash flow you could go with something like a 10 yr full amortizing loan and have some great cash flow and equity at the end of the term.
I don't care for the commercial loan terms right now. They generally won't fix your rate for more than 7 to 10 years and are not fully amortizing which could leave you in a very bad position depending on what the loan market looks like when you have your balloon payment. I personally wouldn't accept a variable loan unless I could handle the worst case scenario easily. What happens to your cash flow when your loan at 4% today goes to 10% in 5 or 8 years. For most people it would end in foreclosure. I stay away from anything that is not fixed rate or fully amortizing for the most part.
With higher end properties your likely to need to pay cash or put a substantial down payment in order have cash flow. I personally like to purchase small multifamily (duplex, triplex, or quads) with a regular 30 yr amortizing loan that have strong cashflow and are in a very nice neighborhood. Now that option may not exist where you are. We have a historic neighborhood here that has gentrified and provides these opportunities. You don't tend to see those type of properties in neighborhoods built after the 50's or so because of the birth of the 30 yr mortgage.
I think in general everyone should be leveraged up some. I'm at maybe 50% which allows a lot of protection and still get some benefits of the leverage. You can buy twice the amount of properties that way.