Without completing understanding your current position, I can answer it with a few assumptions.
1) the seller is a homeowner who is not represented by a real estate broker. Agree on price and terms with the seller and have an attorney draw up the sales contract, as well as handle all escrow, and final closing documents.
2) you have found a townhouse in a new subdivision. The sales agent for the builder will draw up the contract. You may choose to use their settlement company for closing.
3) the townhouse is listed with a real estate broker. You may use that agent (who Represents the Seller) draw up the offer/contract.
If you are concerned about paying a fee to an agent to represent you, this is not necessary. The purchaser's agent will be paid by the seller. This way you would have representation and someone looking out for Your best interest.