I have been separated from my wife since 2006

Frankly, your question is a bit hard to follow.  You are worried that she will request custody BECAUSE she has mental health and drug issues? Answering your last question first, fees are always at issue, and can be requested by either side; from your description, however, it does not sound as if your ex has much capacity to pay anything.  Further, you use the word "separated" and not "divorced."  If so, everything that either of you has -- or owes -- still technically remains community property and debt. You need to consult with a family law specialist.  If you really cannot afford counsel, the local Pro Bono provider is the Legal Aid Center of Southern Nevada, which can be called at 702-386-1070 (or see their information on the web at http://www.lacsn.org/option,com_jcalpro/Itemid,3/extmode,view/extid,15/).  Those that take pro bono cases take them after they have been screened, and assigned, by Legal Aid.  The Reduced Fee Panel sponsored by the State Bar can be reached at 702-382-2200.  Additionally, there are free consultations offered on Thursdays at the self-help center; volunteer attorneys provide 15-minute consultations, for free, on family law questions.  For those that wish to attempt self-representation, forms are available at the Clark County self-help center website, at http://www.clarkcountycourts.us/shc/Supporting%20Documents/self_help_supportingdocs.html.