Judaism is a religion that accepts sincere converts of all backgrounds.
That being said, Jewish law (adhered to by all Torah-observant or Orthodox Jews) requires that a convert go through a process of learning and commitment before being accepted as a Jew.
This process may vary in length depending on the knowledge and commitment level of the person.
In order for a convert to be accepted by the rabbinical court as sincere and ready to join the Jewish community, he/she must have practical knowledge of Jewish law pertaining to daily life, Sabbath observance and the holidays.
Another requirement is that the person must live in a Jewish community for at least a year before completing the process.
The conversion candidate must relinquish any vestiges of his/her former religious beliefs or practices before being accepted as a full-fledged Jew.
The learning process goes much faster and smoother if a potential convert has a rabbi/teacher to learn with and consult with about questions of practice and belief that will inevitable come up.
Navigating the conversion process without this type of support causes a lot of heartache and unnecessary time wasting.
The rabbinical courts want to rule out ulterior motives and may discourage the potential convert much more if he/she does not have the backing of a communal rabbi or mentor.
If a person is engaged to marry a Jew and wants to convert it is all the more important to have an advocate who can vouch for his/her sincerity.
The couple will have to undergo a separation period as well to prove that the conversion in not merely a formality for the sake of marriage.
A married couple in which one spouse is Jewish and the other wants to become Jewish must go through the learning process together and commit to a full Jewishly observant family life.