I would do some pricing a 100 HP CTL if bought new is going to run you around $100k, a brand name mulching head a minimum of $25k, add stump buckets, forestry brushcutters, grapples etc, you see where I'm going. I have a 75 HP CTL and do a lot of work with it for other people as a retirement side gig but I don't jump on jobs to remove lots of 20" trees, I consider myself proficient at lot clearing, property clean-up, underbrushing, forestry mowing, tree and debris removal with a grapple and chainsaw but a 5 acre land clearing job with 20" trees is better left to someone with a track hoe, wheel loader and dozer IMHO. Good luck with whatever you decide but look at what all your options are before you spend a dime. Charlie.