I love my tractor, and all the goodies I have for it, but if all you want to do is cut the grass, I would buy an older model as mentioned like an 8N or something similar which can be had for $3000 or less.
If you get a new tractor figure on $15,000 or more. Lets asssume you mow your 5 acres every three weeks during the growing season or about 10 times a year. Lets look at it over a 15 year period. You would be spending $1000 a year, or $100 every time you cut the grass on your tractor. You could probaby hire somebody to do it for that and not have to mess with it yourself, or have to worry about maintaining the tractor. I think if you did get a tractor you would use it for a lot of other things, or at least I do. I till up a garden, plow and plant 4 acres of wheat, haygrazer or millet, level my driveway with a box blade when it rains, pull out out vehicles when they stuck on the muddy county road, did fence post holes, shred, spray for weeds, move round bales for the horse, etc, etc, etc. I could nto see my self without a tractor, but at the same time I could not justify the purchase if all I was going to do was cut grass on 5 acres.