Pros and cons of leaving boat full time in river water

My wife and I at long last are purchasing some local river front property which has a boat house. The slips unfortunately are pretty narrow with the widest (the one on the left in the picture) being right at 9 feet while my 2000 Sea Ray 190 signature is 8 feet 5 inches wide. There is therefore likely not enough room to put in a lift though I've been researching inflatable lift options which might work.

In the meantime I am considering leaving the boat tied up in the water. I've had the boat since 2009 and it has always been on a trailer when not in the water except for a few times when taking it on vacation to the gulf when its been in salt water for a week.

Neat place. If it is fresh water you should be fine. In Washington, at Seattle Yacht Club people leave their boats in fresh water for years.
Sure lots of piles under the place. From a structural point of view could you remove the center piles at the front by putting in a steal or wood engineered beam to support the deck and the front part of the cottage so you could put your boat under cover in the front part of the boat area.

We boat on the Ohio River and if I leave my runabout in the water for a week it will have significant growth on the bottom. Makes for a lot of drag on a small boat, not to mention a pain to clean off.

Just keep an eye on your anodes till you get a comfort level with how fast they wear. Other than that, would be how quickly the boat starts to grow stuff on the bottom. Being inside a little "cave" can sometimes make it worse since there is very little water movement. But a lot of this all depends on the water you are in. Check with other owners in the area and see how they're doing.

The water lines on the piling suggest significant water level changes that need consideration. The width seems ok for you boat unless wakes will cause it to rock and roll. Need more information to answer the question.

Sounds / looks like a scenario for which the HydroHoist we had installed in our slip is made for (pic attached, hopefully not sideways; no #’s on the boat as we hadn’t received the reg., when pic taken)
All in ours was between $7-8K including EVERYTHING (taxes, shipping, 100% custom-to-our-boat-and-slip-install, etc.)
We look(ed) at it like 15-20% of the total invested in a craft is a reasonable amount to invest in its storage protection, etc.
And, as a knowledgeable captain-neighbor whose gracious and sharing nature is exceeded only by his experience pointed out to us, over a decade that investment is already paying for itself as far as tons of crap not growing on the bottom of the boat. (There is an outboard “jet-type” bass boat left in the water 24/7/365 under a covered dock across the water from us and I finally got close enough to it when the light over the water was just right and I literally gagged when I saw the condition of his prop, let alone his hull.)
We did pay separately to have 110 household electric run out to the dock beforehand but, that is as much for the dedicated dock daiquiri blender as it is the lift!
Obviously nowhere near you - and I only mention in case you need to contact them to find out who the licensed rep/installer is in your area - we used HydroHoist of the Carolinas and cannot speak highly enough of them (if only SeaDeck had such a custimer service eccentric business model! Sigh, smh ...)

Lastly, Best ... o’ ... Success!!!