Also,  I didnt know that hardware stores keep badly mixed paint and sell it really cheap.

There should be Columbus Day sales at the big box stores. 

Again, the BiggerPockets store has some books for this or you can learn by watching podcasts, reading blogs, and interacting on the forum.

For each building use a zippered vinyl money type bag labelled on the outside to store each individual building's keys.To take it a step further which I have not done, keep a rack in the office to hang the tagged original key for each door or padlock. 

Fuel costs, water costs, sewage costs, how much does the store make and what are the costs of running the store, coin operated washer/dryer/showers.

You can buy a test kit at a hardware store but it will generally only tell you what is on the top layer and most lead paint has been painted over many, many times.

It depends on the house, subfloor condition (if tile is going to be a lot of prep, I'll do waterproof floating or try to clean existing tile, sometimes laminate sheet on cheap flips) and current home store prices for most of my choices. 

Looking for alternatives to Home Depot and Lowe’s and other big box stores for a minor rehab I’m doing.

@Samuel S. there are also specialty stores in most states that offer parts, supplies, and materials designed specifically for mobile homes.

Vio doesn't have extensive requirements like regular direct deposits like some online banks require, my one beef with them is their transfer limits are low so I don't store lots of money there because it is slow to get it out if needed quickly.