Tax Deductible Uses for Extra Funds from Cash Out Refi

[Will Johnston]

I recently did a cash out refi on an investment property to pay off the line of credit I had used for the downpayment on said property.

I have about $5k in funds left over, and I'm trying to figure out what to do with them so that the whole amount of interest on my mortgage on the investment prop remains tax deductible.  Here are the possible scenarios I'm considering.

• Pay down the principal on the investment prop.  Of course, if I wanted to do that, I would have just taken out a smaller loan with smaller payments to start.
• Use it to pay down the remaining balance on my line of credit, which was used for the down payment on my primary.  I'm assuming if I do this I can continue to deduct the interest, although I'd have to actually separate out how much of the loan is for the investment prop (98.5ish%) and how much is for my primary residence (1.5ish%).
• Use it to pay ahead on the mortgage on the investment property.  Would this actually be a tax deductible use?
• Buy another investment property.  But I don't have the time to facilitate that purchase at the moment, so I would just have the cash sitting around in an account bearing 1% interest for six months until I'm ready to buy my next door.
  

Other ideas?  I don't have any capex on the property at the moment, although that's not to say there won't be in 2-3 years.

Thanks!
Will