As far as tax strategies with interest - business expense interest is generally deductible if the interest goes directly towards business expenses. If any of that loan amount did not go for business expenses but part goes to personal nonbusiness then its a complicated mess. Just don't do that if you can avoid it. The bill to the CPA null and voids the benefits.
The best advice I got on credit was building a credit history was using a loan when you could have paid cash. This is for newbies to credit. Save up the money for something (plus some extra for interest) take out a small loan, make regular payments and if necessary use the amount sitting in savings to make the loan payments.
I am fond of using interest deferred loans. Apparently most people muck it up and forget to make payments because you don't get phone calls or notices if you don't pay. The real interest on most interest deferred plans is often 29.99%!! If you are one day late, then you get nailed. I see it as no interest loan for X months or X years with a nasty surprise if you don't pay it off on time. I treat it like a loan, because it is one. I calculate my own pay off plan and stick to it. I prefer to pay them off one or two months early. The majority of our appliances packages for our updated units have been purchased on interest deferred plans. My regular payments to these interest deferred plans count towards my credit score just the same a loan payment with interest.
These days the credit services have 'self reporting' systems you can report utility bills, cell phone and other monthly bill payments yourself. That does help. We have seen tenants applying with those self reported bills on their credit reports.
There are plenty of gurus with advice on credit and money. The bottom line is live below your means - accumulate that extra and then start making it work for you. My two favorite books on changing mindset were: Rich Dad, Poor Dad and the Millionaire Next Door. With your experience, skill set and contacts there is bound to be some opportunities you can take a hold of.
I hear Dave Ramsey's courses are very good also.