First Dirt Bike

First off, I would say your too big for either the CRF150 or the XR100. You would be better off to look into something used as your first bike and for $3000, you should be able to get about any type dirtbike that is a couple years old and in good shape. You'll need to give more info on your experience at riding and what type of riding you'll be doing....open trails, MX, tight trails, fire roads, hills, etc.
As far as riding on pavement......don't if you can avoid it and YES, it will eat your tires up fast.

I'd say go with a nice 97-98 kawasaki klx300. Its got plenty of power and I'm 6'0 and it fits perfect. I picked my 98 up for $1900 so the price is right too.

Hi Jadis: Welcome to the party!! You said that htis is your first dirt bike so I am going to approach my answer from the prespective of this being your first bike.
I believe the CRF 150 could be a real good starter bike. The XR100 would be a lot of fun also but I think you would outgrow it pretty quick. Go down to the Honda shop and set on them. See if you can put both feet on the ground while sitting on the seat. For a 1st bike being able to do this really helps (wait till you start riding and you will find out what I am talking about). While you are there sit on the CRF230 and the XR250/XR400 as well.
While you are "playing" on the bikes try to imagine yourself putting around in the woods on them. Lean each of them over a little (careful you dont drop one) and feel the way the weight lays against your leg. If the bike feels "heavy" remember that it is going to feel heavier when you are in the dirt, exhausted from riding and you have to pick it up from a fall. Lower slung bikes seem to feel lighter because they have a lower center of gravity - this makes them easier to ride - especially for the beginner.
Go to the Yamaha shop and do the same thing with that TTR225 that you asked about. Dont be afraid to ask lots of questions about this stuff at your local dealer - answering them is part of the salesmens job!
You have "thrown" a price limit out of 3k. I commend you on saving up that kind of $$$ for a bike - that is WAY cool! Once again I am going to read between the lines and assume you dont know much about bikes and probably have little experience in the mechanical area's? With all this in mind, I would buy a new bike if I were you. You have taken the time and effort to earn enough $$ that you dont hafta worry about getting someone elses problems!
As far as riding them on the street goes - there are lots of DOT approved nobbies out there that wear very well on the pavement and still do a good job for trail use. **please note this** If you are thinking about DUAL SPORTING (using your dirtbike for street use) get the dealer to make your bike street legal as part of the purchase package!
Hope this helps!
Woodsy
Oh, by the way, I have been riding/racing/rippin on these things for 40 years. Have owned COUNTLESS dirtbikes (including the CR500's and KX500's) and I will tell you first hand that I have never owned a bike that at some time I didnt wish for more POWER :) :) :) Start small and work your way up!

I would suggest just browsing through this forum and reading the posts. This question has been asked lots of times and I'm sure you will find some good advice on which bikes fit your criteria. My suggestion for buying used is based upon the fact that since this is the first dirbike you have owned, and your not sure what you want, then you might buy something that you'll grow tired of quickly and want a different one and with a used one, you shouldn't lose much, if any, money by selling it. Plus, your not going to escape the mechanicing(sp?) part anyway with a new bike because the first thing you would have to do is take it apart and grease all the bearings. As far as your pavement requirement, you gotta do what you gotta do but to me, once the leading edges are worn off the knobs, you've lost quite a bit of it's traction and that doesn't take much pavement to do that but maybe a dual-sport would be ok, never tried one. The KLX is actually a good suggestion but if you've never even ridden a bike before(you never said), it may be intimidating to you. But like woodsy said, no matter what you get, sooner or later you will want MORE POWER!
Good luck!

I would look at the XR 250 as well. Its a four stroke so it won't need oil mixed with gas. And as far as a "low maint." bike you won't find much that require less wrenching.

At 6 feet tall you should have no problems and it will give you something to grow into (skills wise) while still being beginner friendly.

Thankfully you are not an "odd duck" like me. When I was a kid my grampa nicked named me "the loner" because I didnt let the "group" make my decisions for me. If I had to "ride" by myself (which was usually the case back then) I just rode. My bikes became my best friends as I wore each one out in rapid pace!! I was then as I am now - a gear head, wrench turning, dirt bike loving FANATIC who was and still is ADDICTED to this life style!!
Of course over a period of tie I developed life long relationships with other folks like myself who I still ride with almost 50 years later!!
Anyway, if you change your mind come on back to DRN. Some of us will still be here!
Woodsy