Keep in mind, the transactional costs of selling a property in Philadelphia with the high transfer taxes and brokerage fees (althoug these are expected to be reduced in light of the landmark NAR settlement that occurred yesterday), adds additional transactional costs, especially in instances where the home was purchased as recently as last year as is the case with your home.

However, from personal experience I would reach out to the HUD section 8 department to give them a heads up about the sale of the property. they will send you a packet to fill out but can't be completed until the new tenant has signed the lease or the current one is transferred into your name.

You folks in California should be buying land for Transfer stations near the ports. 

Most investors are doing LLCs from my experience... but that doesnt mean you have to. there are some liability protections with LLC, along with a little anonymity if set up right. but also some added costs. one suggestion here is just whatever you decide, stick to it. some counties will see a transfer between personal/ LLC or vice a versa as a 'sale' and trigger property tax reassessment.  

Even if you do have assets, and the cost is high, such as in NH where the transfer tax is cost prohibitive, he compares the possible benefits to the actual cost.He has an associate who does the actual return, and with whom he works closely. 

In addition to what Michael said-if you do go ahead with purchasing it, write in the offer that they can not rent out the vacant half, deposit from the occupied side is transferred to you at closing along with prorated rent and get a copy of the lease that has been verified.

I have worked with owners trying to sell or purchase multi-family properties and those types of agreements transfer with the property.

You're basically transferring whatever interest you have in the property to the buyer.

1) make the payment directly from my HELOC account2) transfer the money from HELOC to business checking account, and then make the payment from my business checking account.

If you want to protect your friend's capital as if it were your own, you'd want to:1) Secure the loan with real estate in the form of a deed of trust or mortgage (depending on the state the property is in)2) Obtain property insurance binder with your lender as an additional insured3) Obtain a lender's title insurance policy protecting them (different than an owner's policy) and transfer all funds through an escrow closer or real estate attorney (depending on the state, the requirements for closing may differ)4) Use a real estate attorney who also practices private lender law in the state the property is located in.