There are no problems except for spacial considerations, electrical loads, structural loads, roof configuration considerations, heating and air allowances, and let see, oh yeah, budgeting. sewer connections, access, and exiting to mention a few.
All joking aside, you have not given enough info for a realistic come back. But I can tell you right now, "if you have to ask, you shouldn't do it without help".............
I would at the very least hire a structural engineer to assess your situation. Your footings, attic trusses and the like may not be adequate and need redesigned, especially for a floor load. Not that this will be that costly, but you want to do it right the first time without having junior fall thru the shower floor the first time he goes for a deep cleaning. And an Architect, the guy who can see all the problems at one time while seeing the design aspects as well, would be anther good choice for assistance. All these people will keep you on the straight and narrow.
Another "little" thing you should be aware of is that your municipality will probably require you to submit drawings for their permitting process. If not, you are in worse shape because a good city code inspection department can be a God send. At any rate, you don't want to put in $40,000 and have to tear it down because it is not permitted, or you didn't put in the required tie downs or your neighbor Louise has your site surveyed and you find you are 4" on her property or "what ever". Your architect will take care of all that.
If there are no architects or structural in the area, or even close, and you are up against the wall in a rural vacuum, make sure you hire a good builder who has a goooooood track record. I have known builders who know more than all us professionals put together. Usually they are a product of generations of reputable builders who know their stuff (you see it all the time on the HGTV channel). I wish these guys lived around me.
So, caution is the rule. If you build something that you plan to live in, you can not be too safe.