My question is, for those of you with separate checking accounts for each property, how do you account for and pay common expenses that can't be attributed to one property or another? 

What are some attributes you look for in a sponsor?

The judge magistrate is not going to give you credit for having the lease in your own name.Technically, you might not even have the RIGHT to issue a lease in your own name, if the property is owned by an LLC.I honestly think too many real estate investors attribute magical powers to LLCs. 

If a taxpayer other than a C corporation receives an applicable subsidy for the tax year, the amount of the “excess farm loss” is not allowed for the tax year, and is carried forward and treated as a deduction attributable to farming businesses in the next tax year.

The idea was to find a business where we didn't know a lot, but we each had strong attributes in which to contribute to the whole.

It is good to hear that you recognize this and don't attribute it to your investing expertise. 

Negotiate a notice period of at least 180 days, prior to end of term;  they'll try to work you down to 90, don't be surprised. if the words, "I can't find a new tenant in three months" jump into your head, then stand firm on 6 months.   3) in terms of your OpEx, the things you listed should already be attributed to them, generally speaking. 

Now you can include the labor cost in your total project cost.Let's also assume that your county tax assessor has determined that 20% of your property's value is attributed to the land, and 80% to the dwelling structure (called improvements).   

These expenses I see as more of an overall business expense and can not be accurately attributed to any one property.

Attribute 10% return to your cash, as it's opportunity value, off the top of your rental income and you will quickly discover why dead equity kills a properties cash flow.