A neighboring property, similar to my current rental property, is now on the market at the same price I paid two years ago, with comparable rent.

I live in Belguim so markets are very different here.

You can't arbitrarily decide that you don't want to allocate any of the proceeds to the portion of the property that will create Ordinary income recapture (thus can't be included in the installment sale treatment) - it should technically be allocated amongst all the assets in accordance with their fair market value at the time of the sale. 

I am based in London, UK, so understand this blog does not have plenty of resources for the UK market.

I've seen quite a few car washes on the market and they've always been operated/maintained by the owner.

Or is better to stay off market?

Hire someone cheap and you'll suffer for it.If you are "breaking even" after all expenses and maintenance, then you probably can't afford to pay a professional to handle the marketing and screening.

It really sucks, sorry, it's tough to sell right now with the interest rates, even tougher on the higher value properties, even with extensive marketing which I'm sure your agent is doing.  

I'm in the market for out-of-state properties.

I need to invest in marketing with wholesaling while I know can also make a profit of about $50-$150K in a single flip.