You might have a hard time finding an agent to help you as most don't like writing up lots of low ball offers. For one most are not going to be accepted so it is a lot of paperwork that they know will not result in anything. It also tends to give them bad reputations with other realtors. I don't mind writing low ball offers here and there, but if that is all I do listing agents are going to dread seeing me show their house. Also like you mentioned there is also the concern that the sale will never go through if you don't find a buyer.
My suggestion would be to find a newbie realtor or a fellow investor that has a license and work with them. New realtors generally don't have much going on so they might be more incline to help you out.
I agree with @Derek Faller on this one. Most agents will not want to shoot out low ball offers on homes that will net them only a few $1000s if you close. You also might have to see if you're even allowed to assign a contract using the template that a realtor usually uses.
We have a friendly realtor we use for finding distressed properties. However, she charges a minimum commission for homes we buy. If the buyer's agent only nets $2,000 but she requires $3,000 then we have to pay the additional $1,000 at closing.
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