@Marvin Michel I don’t know the local market, and did not spend much time trying to find current rental comps. But here is what I did find:
You are asking $850/mo. When the duplex was listed for sale last October, it mentioned “Market rate $600+ per side.” (This may not be news to you.) That is still what Zillow shows today - there is nothing on Zillow to say that the property is currently for rent, btw. Ask your agent why.
When googling the address, I do see that it is listed for rent on a number of other sites, and appears to be in the MLS.
Looking at your agent’s Facebook profile, I did not find any rental listings (most importantly, yours) going back a few months - he appears to be looking for buyers and sellers with his posts. Perhaps rentals is not his bread and butter; perhaps he does not know that rental market well.
Besides the property not being listed on Zillow, you may want to open your own account with apartments.com - it’s free - where you can list it yourself, but with your agent’s contact info (or your own.) Let your agent know if you do that (and see my concern below.) I’ve had success with apartments.com in NE Ohio, where I self-manage. If applicants may already have a profile there - and paid for their credit and background check - they may be reluctant to pay more money for that to an agent who doesn’t have access to their apartments.com profile. (Ask your/any PM how much they charge to process rental applications - better not be a turn-off for applicants.) (Because applicant’s credit report would be accessible to you through the site, I would ask your agent to open his own account there, advertise your property, and deal with everything from A-Z - for liability purposes - like he would anywhere else. In my opinion, there is just no excuse not to use tools that are free to you and friendly to your applicants.)
Apartments.com does have this other listing two blocks away (I don't know the area, so it may be less desirable than yours) becoming available on June 10: https://www.apartments.com/2-br-1-bath-house-2024-hill-avenue-middletown-oh/0wj61x3/ Unfortunately, it is bad competition: it's a 2/1 SFR for $825/mo, allegedly "fully updated" inside.
Incidental to the above apartments.com listing, I would contact the management company behind it to see if they could opine on your property, as @Bill Brandt suggested. While I have not done any business with them - I invest elsewhere in Ohio - if this is the Dix I’m thinking about (I don’t know how many PM companies may be working in Butler County whose name starts with that word,) they’ve been recommended to me and are a large player in the area.
Assuming that free Internet is available in your area for free to customers below certain income level, that perk may not be a big deal - hopefully, it does not cost you much.
This is all to say that to me - from far away - it looks like you/your agent may be asking too much. But follow Bill’s advice.