I did a four year apprenticeship of cleaning oil boilers and crawling into attics, I think I can handle a potential buyer/seller lead saying no to me being their agent.

Zillow, trulia, and facebook seem to be great resources that they're not using, so I can add those as well. it also seems that it takes a month for them to clean, then they advertise the next month, for a longer turnaround time. 

It is a large 2 story older home and needs about 2500 dollars in roof repairs, due to gutters not being cleaned out and Facer boards rotting away.  

The only real risk to you is the fact that the property will now have to appraise for $61,000 in order to get this deal done, rather than $58,500 if the offer were "clean".As a contingency, you should discuss with your agent what your plan will be if the appraisal comes back short. 

Put all of the information on a nice clean spreadsheet then shop the deal.  

Unless tenants have nice stuff and keep the place clean it's hard to get top dollar for occupied units.

If the place is not cleaned or rent is not paid, they are both liable.

Yes, there are more costs such as furnishing, cleaning, management, etc., and I do most of the cleaning myself (but have used crews when I cannot get out of the office), but the profits far outweigh any costs or time I put in.

I would not do anything to it aside from a deep clean.

People who can pay top of the market are usually the ones who care to live in a clean and nice space, they will take care of your house.