Hey Shawk

I'd stick away from buying someone elses lace unit especially if it isnt your size or colour to start of with. Lace units can be cut down but considering your new to this then I wouldnt recommend it as its quite a task (i've tried it before).. and if you die your hair you'll have to keep doing your roots coz they will regrow to your normal colour making it look pretty wierd.

also keep in mind that a good custom or stock lace unit will have a welded edging to the shape of the template or size specified for it, this prevents tearing on the edges of the lace so if you cut it down then you lose this feature.

I know your trying to save some cash but at the end of the day you may end up paying double if the first one goes wrong. If price is an issue just google different hairpiece sellers and see what deals you can get, maybe even email them to see if they may give a discount for your first purchase (sample / trial) its worth a shot.