Welcome to TBN. You'll find plenty of good advice here... in fact you already have some from the previous posts.
Someone mentioned the Grand L models instead of the M series. I would second that idea. The L's would be more transportable, but would still handle your mowing and dirt moving needs. They would also give you the option of hydrostatic transmission... easier to operate. You don't say how much acreage you are dealing with, but the Grand L (
L4740 and up) would be hard to beat for, say, under 40 acres of actively maintained property, might be better choice for a new user vs.
M5040. The M series are excellent farm oriented tractors, that would do your work, but the Grand L's are basically designed for your type of situation... part-time user, variety of chores including mowing and dirt work, ease of operation, short wheelbase.
Are you planning to transport that new, costly tractor to your property when needed or do you plan to keep it there permanently? If you will be transporting it, you'll need to think about a trailer and tow vehicle.
If you will be storing it on-site, you'll want to consider how to secure/shelter the tractor while you are not there. Leaving it and your equipment sitting out in the open is hard on the equipment and an invitation to theft. That may speed up your construction timetable, or maybe you have a neighbor who will allow you to store your equipment.
Hope this is helpful. Others will have more ideas. Best of luck... sounds like a dream is being realized.