Environmental risk is considerably higher too.....failed tenants frequently leave behind nasty messes.

I had to consciously do that for myself, because I enjoyed the sense of accomplishment of doing the work, but I knew my time was better spent doing other things. 

I know many of you may think how can you do that ,well fortunately  we happen to be in an extremely relaxed lending environment ,ive been in this business for 30 years and this is only the 2nd time i;ve seen real estate lending this relaxed ,for you old timers ,i know you can remember when their was no seasoning of title , in that period i was able to acquire 20 properties in 6 months ,moving right along ,heres the formula 1) find a property that needs a rehab in a b or c+ neighborhood,determine that after the rehab you will be at a 65 to 70% arv,next after you've acquired and rehabbed the property refinance it ,heres the example ,$45,000 purchase ,$30,000 rehab ,finished value $125,000,now you have a couple of options,you can refinance the property in 30 days at a 70% ltv,or you can refinance it later at an 80% ltv in 90 days,,using the example at 70% your cash out is $87,500,lets assume that your settlement costs were $8000 per transaction for the intial purchase and refinance,this equals $16,000 ,your cash out is $12,000,which leaves your out of pocket at $4000,this would be your total outlay,assuming that you rented the property and had net revenues of $500 a month your total return yearly would be $6000 monthly,your roi is 50%,now if your roi wasn't this high ,let say 30% annual return ,i don't think you would be too mad ,however you have another option and if you are not in a hurry you can refinance in 90 days at 80% ,when you refinance your cash out would be $125,000x80=$100,000-$75,000=$$25,000-$16,000 would be $9000,,so the $64,000 question would be how much did this really cost you,rinse and repeat this formula over and over  and you will be a happy camper              

No affiliation, but https://www.oeservices.net/environmental-site-asse...https://www.wh-m.com/service/phase-1-environmental...I have used Terracon for my clients and very pleased with their work in Texas.https://www.terracon.com/services/environmental/environmental-site-assessments-and-investigations/

I would probably avoid th ecomplications and environmental requirements of a actual marina and simply install docks for the tennats boats.

The MLS systems I belong to made a conscious choice to allow entry-only listings. 

In Texas, I typically use fee attorney's (who represent the title company) because I'm document conscious and the attorney seldom fights me on document revisions / deletions like an escrow officer often does.

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Environmental compliance?

Done right, a grow op can be done with a small environmental footprint, but as @John D. points out, there are structural limitations to the house that might not allow best practices, in which case a lot of harm can be done.