More importantly, negotiating requires a serious attitude. People who aren't ready to part with their money are seen as weak. That's a death knell in negotiations. It is imperative to get out and look at vehicles. However obvious this may seem, often people are unwilling to step out and see what's available.
Agoraphobia has no place in the car shopping and negotiation process.
Without shopping, there is no way of knowing the selection, condition or competition for the models under consideration. And, without that information, there is no basis on which to compare cars and know a good deal when it presents itself. It is impossible to cogently talk price until the extent of needed repairs, if any, and the associated costs are determined. The vehicle has to be worth owning and that might take some work. Refusing to discuss price until the vehicle has been seen by a mechanic is also a tactic that buys time.