While we are familiar with the Propionate ester the remaining three esters that create Sustanon-250 are almost always found as part of a mixture or compounded anabolic androgenic steroid .
Developed by Organon, the original idea behind Sustanon-250 was to provide a testosterone form well-suited for hormone replacement therapy that would only needed to be administered once every few weeks and for all intense purposes the idea was a success. For the performance enhancing athlete Sustanon-250 can be a fine choice but the idea of injecting only once or twice a month is not applicable here. As a performance enhancer this testosterone like all forms will need to be administered on a more frequent basis. This mixture carries with it two fast, short esters, Propionate and Pheylpropionate, a longer more moderate ester Isocaproate and the very slow and long Decanoate ester. In order to keep testosterone levels stable and at their peak most athletes will inject Sustanon-250 at a minimum of every 3 days and more commonly every other day for optimal results.
For more info see: Sustanon-250
Of all of these options none of them are outright safe; any site that allows you to buy testosterone by paying for it on their website you need to run for your life, as to do this you will be giving your credit card information to who knows who. As for gym dealers, this can be a tossup. If you can find a gym dealer who is not a middle man you may have a good source on your hands but understand if he gets into trouble himself he will more than likely sell you out at the first chance he gets if it saves his ass even slightly; most of them are scared and will not hold to any honorable line. Without question, when we buy testosterone on the black market there is no safe bet but there are some good sources out there who keep a low profile, use secure servers and email accounts and who are generally safe for most. In the end, understand, such purchases are illegal in many countries so if you choose this rout the risk is on you and you alone.
Like other AAS, drostanolone is an agonist of the androgen receptor (AR).  It is not a substrate for 5α-reductase and is a poor substrate for 3α-hydroxysteroid dehydrogenase (3α-HSD), and therefore shows a high ratio of anabolic to androgenic activity.  As a DHT derivative, drostanolone is not a substrate for aromatase and hence cannot be aromatized into estrogenic metabolites .  While no data are available on the progestogenic activity of drostanolone, it is thought to have low or no such activity similarly to other DHT derivatives.  Since the drug is not 17α-alkylated , it is not known to cause hepatotoxicity .