Hi Oxford, this is a good place to begin your search for resources, including agents. There are a few that do offer this type of guarantee - so take the responses you get here as a start, also call local brokerages to tap additional resources. Interview the agents, get a very good understanding of their "guarantee" program and then you'll understand your options, the terms of the guarantee, and can make a good decision.
I recently attended some training and there were a few agents that do offer this type of guarantee - evaluating the property's marketability is an important part of their evaluation of whether to take it on. By going through the process of evaluating options and agents, you will get a good understanding of whehter this route is possible and if so, the best path to take.
Good luck to you on both the sale and purchase.
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