Maybe the work of Phillipe Caille can be useful for you, i add the link of the book in french,

https://books.google.es/books?hl=es&lr=&id=cb4vD7MG4PYC&oi=fnd&pg=PA11&dq=caille+philippe&ots=_0D7o0Plr1&sig=NvH--gVjlu5iRM2qFzwa_HtG40M#v=onepage&q=caille%20philippe&f=false

also the work of judith butler about the queer teory maybe can be useful for you, i add the link of one book.....

https://books.google.es/books?hl=es&lr=&id=UczySqq19AIC&oi=fnd&pg=PP1&dq=queer+butler&ots=scVOguMW3H&sig=mlHNvZ1bF0hZQ80YAHWi8F-fIl8#v=onepage&q=queer%20butler&f=false

Hello Prof Pimor

These might be fairly relevant, although the first was published quite a long time ago (I have not referenced any of the papers that were older than this one):

Nyamathi, A. M., Dixon, E. L., Robbins, W., Smith, C., Wiley, D., Leake, B., ... & Gelberg, L. (2002). Risk factors for hepatitis C virus infection among homeless adults. Journal of General Internal Medicine, 17(2), 134-143.

http://onlinelibrary.wiley.com/doi/10.1046/j.1525-1497.2002.10415.x/full

Stein, J. A., Nyamathi, A., Ullman, J. B., & Bentler, P. M. (2007). Impact of marriage on HIV/AIDS risk behaviors among impoverished, at-risk couples: A multilevel latent variable approach. AIDS and Behavior, 11(1), 87-98.

https://www.researchgate.net/publication/7316956_Impact_of_Marriage_on_HIVAIDS_Risk_Behaviors_Among_Impoverished_At-Risk_Couples_A_Multilevel_Latent_Variable_Approach

Smid, M., Bourgois, P., & Auerswald, C. L. (2010). The challenge of pregnancy among homeless youth: reclaiming a lost opportunity. Journal of health care for the poor and underserved, 21(2 Suppl), 140.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3037014/

I could only access the abstract of these papers:

Rayburn, R. L., & Corzine, J. (2010). Your shelter or mine? Romantic relationships among the homeless. Deviant behavior, 31(8), 756-774.

http://www.tandfonline.com/doi/abs/10.1080/01639621003748803

Stevenson, C., & Neale, J. (2012). ‘We did more rough sleeping just to be together’–Homeless drug users’ romantic relationships in hostel accommodation. Drugs: education, prevention and policy, 19(3), 234-243.

http://www.tandfonline.com/doi/abs/10.3109/09687637.2011.644824

Very best wishes

Mary

Article Impact of Marriage on HIV/AIDS Risk Behaviors Among Impoveri...

Hello Tristana

You can google using the terms "survival sex" and "homeless". Be cautious though because you may hit some nasty sites. Here is the result of a google hit that you might want to follow up (Best wishes, Paul):

Correlates of Engaging in Survival Sex among Homeless Youth and Young Adults N. Eugene Walls

Graduate School of Social Work, University of Denver

Stephanie Bell

Prax(us)

Using a sample of 1,625 homeless youth and young adults aged 10 to 25 from 28 different states in the United States, this study examines the correlates of having engaged in survival sex. Findings suggest that differences exist based on demographic variables (gender, age, race, and sexual orientation), lifetime drug use (inhalants, ValiumTM, crack cocaine, alco- hol, CoricidinTM, and morphine), recent drug use (alcohol, ecstasy, heroin, and methamphe- tamine), mental health variables (suicide attempts, familial history of substance use, and having been in substance abuse treatment), and health variables (sharing needles and having been tested for HIV). In addition to replicating previous findings, this study’s findings suggest that African American youth; gay, lesbian, or bisexual youth; and youth who had been tested for HIV were significantly more likely to have engaged in survival sex than White, hetero- sexual youth, and youth who had not been tested for HIV, respectively. Implications for interventions with youth and suggestions for future research are discussed. 

In context of India Prof. Amita Bhide from Tata Institute of Social Sciences has relevant studies on the same topic.  

Parity magazine is Council to Homeless Persons’ (CHP) Australian national publication, examining homelessness from personal, local, social, national and global perspectives. There may be something about those topics there - here's the link

Susie Costello

http://chp.org.au/services/parity-magazine/

Il y a la recherche de l'observatoire du samusocial de paris, qui est l'une des enquêtes sur le site :  http://www.samusocial.paris/nos-enquetes et qui a donné lieu aux publications suivantes, mais vous devez déjà connaître :

 "Sexualité et relations affectives des personnes sans domicile fixe - Entre contraintes sociales et parcours biographiques", Oppenchaim N., Pourette D., Le Méner E., Laporte A., Sociologie,3.

"Inclure les exclus comme objets de préoccupation scientifique : l’exemple de la vie affective et sexuelle des personnes sans domicile fixe", Oppenchaim N., Pourette D., in Lazzeri C., Nour S. (dir.), Reconnaissance, identité et intégration sociale, Nanterre, Presses universitaires de Paris Ouest, p. 261-276.

"L’hétérogénéité des expériences affectives et sexuelles de femmes vivant sans-domicile-fixe", Laporte A., Le Méner E., in Les femmes et le Sida en France – Enjeux sociaux et de santé publique, Médecine Sciences, 24, 2, p. 41-47.

"Améliorer les conditions de vie affectives et sexuelles des SDF", Pourette D., Laporte A., Le Méner E., Oppenchaim N., La santé de l’Homme, 392, p. 42-43.

Sinon, il est fait allusion à ce thème dans l'ouvrage de Snow et Anderson, "Down on their luck"

merci Beaucoup