One thing to consider when you are budgeting is the taxes and insurance.

My insurance and property taxes are also set up in this manner. 

The less colors you use the easier it is to buy bulk and save $$.

Is your DSCR ratio greater than 1-meaning are you cash flowing (according to the lender's criteria of mortgage, property taxes and insurance (and HOA) if applicable).

I love Leveraging OPM (Other Peoples Money) My opinion is to use a HML, and save your money.

I am in search of an efficient system  to track my rental properties regarding income and expenses to make it easy for my accountant at tax time.

I use Innago as a management program which allows different taxable entities for the rents, which would assist when it comes tax season.

Look at lists of properties that are on the Sheriff Sale, and Tax Sales, as some of those could have assumable mortgages, and provide a list of potential assumable mortgages, where the owners are potentially losing their properties.David KrulacBigger Pockets Podcast guest #82  

You need to understand the tax regulations on both sides of the boarder.

Taxes in these zip codes might be higher but they're great long term holds with steady appreciation.