One has been rented out for four years same tenants and the other one is newly acquired and have been trying to find the best platform to market it (furnished finder, Zillow, Airbnb, etc)Would the suggestions from the real estate investors be excessive or something to look into?

There are no laws restricting mark-to-market rents. 

Our first year out was crazy good renting for $3300 when market rate was around $2100, but by mid 2023 and 2024 it felt harder.

I know this is not true because I've used IDI data since 2019 and it's the best on the market. 

Any turnkey companies specifically you're referring to?

Airbnb brand is strong 💪 Correction, AirBnB marketing is strong. 

I wish there were a hundred of these on the market.

We have final site compliance plans in Columbus Ohio for large development projects and the only people that can do them are either an architect or a civil engineer. an architect is more versatile but the real knowledge is a civil engineer but you need to be able to stamp it for accuracy and you are putting your professional experience on the line. it has nothing to do with zoning. civil engineers don't really help with zoning that would be done by an entitlement group or zoning attorney. degree is probably mandatory before you can become a professional engineer but yes there is incredible demand for those services in our market. for subdivision development as well this is amazing skillset to have.  

I purchased a duplex (Austin, TX) at peak market prices in 2022 for $720k.

If, through the process of renovating the property, the market shifts, do you have an alternate plan for the property, whether it be to live in it until the market improves, or convert it to a rental property, etc.