A little insight @Brandon Williams, Shorewest pulls data from the MLS's IDX feature, the most up to date data for non Realtors is Realtor.com.3&4 units tend to be in high demand for the casual investor, the debt level is not terrifying, and most owner own maybe 1 or 2 properties, as a diversification play in their retirement strategy, this makes them highly desirable, and pushes the price up.

I work full-time as a data specialist and I am currently in school to finish a real estate course to receive a real estate sales license and even a broker's license further on down the line.

Are there any good ways to ensure this?

Offering a discount on monthly rent will more or less help close the deal and ensure I get a good renter. 

To ensure for $250K replacement cost assumes a from scratch newly built building assuming the old one is not salvageable (e.g. total house fire).

Where can I get reliable data? 

Of course some properties are still good investments with tight margins, but I would just double check all your other numbers (expenses) to make sure you're estimating your cash flow conservatively, or, if possible, based on actual historical data. 

I hope you looked up crime data before buying

The Operating Agreement must contain language sufficient to address IRA-related issues concerning Prohibited Transactions (26 USC 4975), The Plan Asset Rules, the allowance of subsequent or additional Capital Contributions and Unrelated Business Income Tax (including language that ensures that the Manager of the LLC will prepare and file all necessary tax forms with the appropriate taxing authorities, Federal, State and local).

I did so to ensure I’d have ample liquidity to jump on other deals when they come up.