I have been riding an old mountain(1990's) which would be the equivalent of a hybrid by today's standards on the streets around my town (20-30 miles per ride since that's all my legs can take on that bike). I'm looking to make the jump to a road bike but am interested in competing in tri/duathlons, as well as competing with my friends on the rode. I've been looking at the Specialized Tarmac/Roubaix/Allez Elite as well as the Trek 2.1. I loved the feel of the Tarmac as a road bike but am second guessing myself on purchasing a road bike to ride tri/duathlons with. Most people I've seen race tri/duals have TT specific bikes. Ive narrowed it down to these couple Q's.
1) Is it crazy to get a TT specific bike as my first road bike?
2) Should I just get clip on aero-bars and attach them to the conventional road bike?
3) Is there a model/line of bikes that can be converted between the two styles?

Any input would be greatly appreciated. Thank you.

PS. I also have a budget as I am in my second year of college. I'm looking for something at most 2000, which would be the 2009 tarmac elite.

Get a road bike. It's much more versatile. You can add clip-on aero bars for tri's later.

It's very difficult to ride tri/tt specific bikes all the time.

I agree. Go with a road bike. Buy one that takes a standard seatpost (not proprietary) and have a forward tri-style post for triathlons and the normal one for road riding. Profile makes an aerobar that has flip-up arm rests so that you can reach the top of your handlebar when you're not using the aerobars.

Alternately, see if you can find a 2008 Cervelo Soloist on closeout. They have a seatpost with a removeable clamp. All you have to do is buy a second clamp and saddle and swap those out. That way, you don't have to adjust your seat height each time.

buy rhe best road bike you can buy. Enjoy it and if you want to try a tri/biathlon do so. Once you get the bug you will be better able to decide what it is you need

You'll have a heavy bias toward the road bike on a road bike forum, and you'll see similar bias if you ask on a triforum.

I'm a triguy, so I'd say the TT bike is fine, and could even be recommended, but having just recently got only one TT bike myself to ride (and a fine one - the Cervelo P2C!), I feel that you should answer these questions first:

1) How often do you group ride? If you group ride regularly, the road bike is better. More welcome, and much easier to use in the group due to the integrating shifter/brakes ("brifters"). True TT bikes can be annoying for you to shift in groups, especially in traffic, as the gearshifters are on the barends and brakes on the horns (drops), so you're constantly moving your hands. That said, I've ridden with several groups recently, and have had zero problems with the tri-bike aspect, and can fit into the group ride with no complaints/comments from others.

2) Hills - I didn't expect to be training as much as I am in mountain territory, but I find myself regularly doing weekend climb rides of avg 6-8% inclines, with 10-15% sections. Tribikes are harder to climb with, for sure. If you're going to be doing significant regular climbing, I'd strongly recommend at the least, compact cranks. Even the Cat3 riders in our group ride don't ride the race gearing 53-39/12-25 up those hills, and use either compacts or easier gearing. I'd say the tribike is totally fine for anything 6% or under; it's the long sustained 8%+ sections that will hurt on the tribike due to the geometry and aggressive gearing.

If you're riding mostly moderate hills (not long big mountain climbs 8%+), the TT bike will work fine and will likely be faster in aero. Most of the trifolks I know, both in person and online, mainly race bikes in tris (no crits, cyclocross, etc.) so they absolutely recommended just going with the TT bike, period. Racer roadies tend to do a wider variety of races (crits, etc.) and for those, you absolutely need a road bike, so I understand how they absolutely recommend going road bike. In my opinion, the road bike is definitely more flexible in terms of training options, especially with a compact crank gearing for hills. But then again, go to the triforums, and you'll hear tons of folks who have great road bikes, yet realize that since they're racing in tris, they should be training and racing on a tribike, despite its limitations.

Eventually, you'll probably get both to have best of both worlds. But if you know you'll be primarily tri, go TT unless the two conditions above indicate that roadie would be better.

so how much difference is riding on the bullhorns of a TT bike compared to riding the hoods of a road bike?

On the hoods, you can shift & brake.
On the bullhorns you can brake, but to shift, you must reach to the aerobars.

Another one for the road bike, and I work with triathletes.

i made the decision of a roadie and im happy.. i have my first sprint tri coming up and ill let you know how it goes. I spent about two weeks on a quintana roo seduza(buddys bike) and it was WOW but still happy i went with a specialized tarmac elite with some aeros!

good choice.

Does ne1 own a Specialized Transition Multisport? I've found a new 07 model in my size. It looks like it has the tri-geometry with clip on aero-bars, but it also has drops and is set up like a road bike(shifters on the drops.