I own a timberking b20. It's similar to an lt40 hydraulic. It's a very nice machine. It's also for sale. PM me if you want details, by the way.
I can say this. I like the hydraulic functions of my mill. When I bought it I didn't have a good tractor with a loader. If you've got that, or a skid steer, the hydraulic features may not be as important.
I can also say this, in my area, no one wants to pay for custom milling. Maybe that's not an issue for you. If you're planning on milling logs and selling lumber that's a different plan. Of course, in that case you'll need a kiln or a yard for air drying and a large area to store lumber. You'll also need an industrial planer.
On custom milling, though here's my experience: the mill is cool, and does good work. It's also dangerous (mostly because logs are dangerous), noisy, and costs money to run. They require occasional fine adjustment and there is no mill immune from breakdowns. They require skill to operate. In my area, folks are VERY reluctant to pay over $40/hour to have the mill operate on their land. To do a job, you have to hitch up your mill, load up your tools and equipment, drive to the job, and then undo all this afterwards. All this takes time, which needs to be figured into your price. Also, you need to account for fuel, lubricants, blades, maintenance and INSURANCE. Insurance is huge. Before you do ANYTHING else, call your insurance agent. When our agent got wind of a sawmill he basically said he needed to cancel our entire policy, farm, home, business everything. I'm sure you have insurance already, but try calling your agent and saying "sawmill", I dare you.
So, total up these costs, figure in depreciation (if you dare), and then add your wage. If you think you deserve make more than $2/hour to work all day on a noisy, stinky, dangerous machine, you may want to reconsider your plans. If people would pay $75-100/hour it might work out. At $40 it don't.
Honestly, in my area anyway, a tractor and a bush hog would make way more money. Less insurance cost, less fixed costs, more potential customers, more relaxing to do. Way way less thinking and no math. No take measures either.
I'm not trying to crush your dreams. Mills are cool. I like mine. Honestly, though I wish that someone has grabbed me by the collar and told me what I just told you before I bought my mill. The companies that sell them do a great job of showing you some successful mill owners. That's not the only side of the story, though.