Hi man,
I can't help you directly with yoga sources but I can give you an advice, confirmed on base of experiences from past.
Because you are seeking on long term I suggest you to "risk" some money for few individual hours or to take yoga course (at least here in Slovenia we have few of them). That way you will really learn basics much better, like Deborah already said, instructor can check your proper form and guide you. If you do this home alone, you can't be concentrated on everything and you can easily miss some important things, especially when you start with something
completly new; you just can't be concentrated on breathing, relaxing, proper form etc., until you reach some level of experience. My ex is pilates instructor and I know how it goes if you learn from videos by yourself or instructor teach and check you. Some things looks quite simple but they are quite complicated in fact.
Second reason why you should invest a little more at start is that you will get much better insight in it, you'll know better to decide what is good and reliable source and what not, you'll better know what and where to look/search further for more knowladge and exercises. Starting expense is neglectable in lifetime usability ;)
BR, Gregor