As to get to University Paris XIII from Paris you will need to take the suburban train at Gare du Nord it is convenient to stay at a place reachable by a direct subway line from Gare du Nord.
Suggested areas for hotels are thus: the Gare du Nord area, Place de la Republique (take line 5).

Here are a couple of addresses:
  • around Place de la Republique:
    Hotel de Nevers: 53 rue de Malte (11e arr.), tel: (+33)1 47 00 56 18.
    With shower: 44 euros, without: from 34 euros.

    Quite basic, but cheap:
    Hotel de Vienne (*): 43 rue de Malte (11e arr.), tel: (+33)1 48 05 44 42.
    With shower: 42 euros, without: 28 euros.
    ( subway station: Republique line 5)

  • around Gare du Nord:
    the area is perhaps not very charming, but the location is convenient.
    Hotel Paris-Liege (**): 36 rue de St Quentin, tel: (+33)1 42 81 13 18.
    With shower: 45 euros.

  • around La Villette (19e arr.):
    more confortable:
    Hotel Ibis La Villette: 31 quai de l'Oise (19e arr.), tel: (+33)1 40 38 04 04.
    (subway stations: line 7 Corentin Cariou, or line 5 Ourq)
    room for 1 or 2 persons, with shower: 62 euros.

    To find your way in Paris (route finder): route finder
    To get to university Paris XIII (Villetaneuse): see here