Hey! Congratulations on your new land! We'd all love to see some pictures.
Half the fun of property and toys is having just what you enjoy. So if you like the Yanmar I'll start there. I assume you mean the YM135D, sometimes called the YM135d - which is the 4WD version of that tractor. The YM135 (without the "D or d") was/is a 2WD machine just as durable, but mostly useful on very flat land for mowing or for rototilling....but not for traction work like blading, or plowing or pulling. There weren't many of the 2wd version sold. A tractor that small really needs to be 4WD.
The YM135D is a jewel with legendary durability - especially when coupled with the matching loader. That was the most common configuration for good reason. Take a look at the Yanmar Specific group here on TBN and you'll be surprised at the number of active helpful members. Like all of the older tractors that have stood the test of time, it will do some honest work for you and should be worth whatever you have in it for many years yet.
That said, the YM135d is just too small to be the only tractor on more than an acre or two. It just right coupled with the factory loader and used as a "chore tractor" around the acre that has the house and barn....and will get you by on non-tillage 3 pt work for a year or two while you get to know your land. I know this because I have the YM165 version (essentially the same machine) and have for many decades. It has built a foundation, pond, and several other projects - but it took forever. Changing to turf tires to widen the stance helped the stability - always a problem on small compact tractors.
My suggestion is to find someone that you trust and plan to spend a few weekends looking at tractors. Don't be shy to take a few home and use them. It won't hurt a good tractor to do so. An honest assessment of your own mechanical inclination is probably very important at this point. And of course every time you look at a tractor take some pictures and run it past the group here. That will help you with the decision and we will enjoy it too.
Some hints: Don't go out there expecting to find a great dollar "deal". Look for quality instead. Unlike in the markets for autos, trucks, land, or most tools.....tractor prices are exasperatingly solid. Accept it; it will eventually work in your favor.
Don't be afraid of an old and well cared for tractor. BTW, good tractors live under cover of some sort; never out in the open. Tractors wear slowly and change slowly too. The only large improvements I've seen since the late 1960s are that more small tractors have hydrostatic transmission and power steering. But the older geared tractors are still with us and doing fine. And manual steering won't hurt you.
Checking out a used tractor: Take it home for a week and see how it does. If you can, drive it home even if it takes an hour. Oddly enough, much of the needed maintenance on a tractor shows up more obviously when roading it at 12 mph than when working.
Bottom line: if the YM135 is 4wd, in very good condition, and it has a loader then you might as well give it a try. You already like it and it is a popular smallish tractor. It will do some work, and in the process you will learn. If it doesn't have 4wd, good condition, and a well-matched front end loader you should go directly to the 20 to 40 hp range of tractors more suitable for 14 acres. Be wary of older 2wd US farm tractors with loaders that are too large - that makes for poor traction and difficult steering. Whatever you do, be SURE to get a tractor that has a standard three point hitch and a drawbar! Definitely no deviations from that are allowed!!
Most of all, have fun with the search.
rScotty