But now he is staying so we decided to play the cat card, and told him that per his lease pets not allowed and if he would like to keep it we will need to amend his lease to include additional $100 pet rent plus collect additional security deposit.

They have an ID card with your picture on it so you cant even sneak in guests. 

I see they suggest offering the tenants the option of paying by Credit Card.

I usually suggest new property owners setup a business before they even close on a property and then use a business credit card for all expenses moving forward and also for them to link it to Quickbooks so everything is automatically tracked for them.There are a lot of nuances and strategies but this is a 30,000 foot view of why you should opt for business>personal

So I was buying repair items for my rental at Home Depot and I forgot and used my personal debit card...is there a simple way of expensing the items and paying for them out of the business account AFTER the fact? 

Much easier to delude one self into purchasing a "mentorship" program for $30,000 or more ("put it on your credit card; you'll make it back on your first deal so it really won't cost you anything") and believing that after a "3 day boot camp" you'll be able to compete successfully with people who have the education, knowledge, experience and track record and have been doing it for years.  

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Lastly, finance the rest on a credit card.  

I don’t have any credit card debt but I have several other bills that are like utilities that are getting past due and I am literally flat broke.

I've heard in the US, you could get a credit card from home depot and there was no interest for the first 6 months.