Do your practice and all is coming.
Yoga is 99% practice and 1% theory.
Body is not stiff, mind is stiff.
It would be a shame to lose the precious jewel of liberation in the mud of ignorant body building.
Anyone can practice. Young man can practice. Old man can practice. Very old man can practice. Man who is sick, he can practice. Man who doesn't have strength can practice. Except lazy people; lazy people can't practice Ashtanga yoga.
Yoga is possible for anybody who really wants it. Yoga is universal.... But don't approach yoga with a business mind looking for worldly gain.