Maintenance is an operating expense and should be paid using rental income.

One mistake I made due to having enough money to spare when first starting: My chosen marketing method for getting motivated seller leads was direct mail, and I spent a small fortune on that without really tracking and evaluating the marketing ROI, tweaking accordingly, and trying a different version.

You are on the right track in seeking information from more experienced investors early on in your endeavors.

If you lease does not prohibit operating a business from th eproperty it does not matter.

I agree with Carl Fischer that should follow your contract and schedule to ensure work progress and payment stays on track.

One added detail is this other couple are family (my husband's sister) so we need everything written and laid out clearly but with the assumption we will operate within these boundaries without going to court...meaning we don't need every word to be air tight but need it to be clear cut (as a side note I'm not interested in hearing about horror stories of doing business with family, I have done real estate business with family for over ten years and am fine with it). 

Other houses that I have that are strongly cash flowing I can use to supplement my income and help with operations costs when starting into the MF property.I have also invested in a pair of fourplexes, which is not quite the multi-family model (which is 5+ units) but a good starting point with a larger supply of units so a vacancy does not hurt quite as much.

The ones who don't end up being very good end up quitting because they aren't making money and the ones who just send MLS listings may be on that track.  

It depends on the bank @Yash Bajpai , probably a local bank which is all over the state will be better then very small/ family owned bank type. this are much stricter and often just want to work with Local state residents with some track record. you could contact a local mortgage broker that could shop for you.And, if you are planing to buy in this state it is wise to open a checking or saving bank account with one of the local banks.

You are correct on the liability protection with the title in your personal names but an LLC will provide you guidelines of your operating agreement.