A buyers agent is a person that look a property for you. e.g. You tell him/her: I need a property with this number of bed; bath; in this or that area; at about this or that price with this or that capital growth and or yield. The buyers agent will do all that work for you in finding a property that fits within your selection criteria and will also negotiate the price with the vendor. It's understandable that all this work will attract a fee.
In short, a wrap is a totaly different concept from the above. It's a contract inside (wrap) a contract.
e.g.
You buy a property and then, you on sell it to someone else. The difference is that you provide the finance to your buyer. You act like a Bank for him/her. In so doing, your contract with your buyer has a higher interest rate that the one you have with your Bank. That difference in interest rates if your profit (the same way Banks do money when they lend). Simple, your buyers let's say pays you $100 a week and you pay your Bank the $80 a week they are charging you for the loan. You get to keep $20.
Hope this help,
James.