Four advocates for homeless rights were arrested Tuesday night when they refused to leave the Capitol Hill office of Rep. Joseph Kennedy. The two men and two women, charged with unlawful entry, were among eight Boston homeless-rights advocates who staged an all-day sit-in at the Massachusetts Democrat's office in an attempt to force the congressman to endorse a $20 billion housing bill. The bill, sponsored by Rep. Barney Frank, D-Mass., would provide 7.5 million units of affordable housing. It rivals Kennedy's proposed Community Housing Partnership Act, which would allocate $500 million in federal matching funds to non-profit affordable housing projects. After meeting with Kennedy in his office, eight demonstrators said they would stay put until the congressman pledged to support Frank's bill. The group had been protesting inside Kennedy's office since 11 a.m. and four refused to leave when asked by the congressman's staff, said Capitol police officer Dan Nichols. Nichols said they are scheduled to be arraigned in D.C. Superior Court on Wednesday. They face a possible $500 fine and@or up to six months in prison. Jim Stewart, an organizer for the protesters, had said earlier the group of constituents, four of whom are homeless, traveled to the Capitol in hopes of ``putting momentum behind the Frank bill'' by lobbying members of the Massachusetts congressional delegation. ``The least we can do is risk arrest here until we convince Joe it's the right thing to do,'' he said, adding that Kennedy's housing bill is ``inadequate to the need'' of the homeless. Aides to Kennedy, who is a member of the housing and community development subcommittee, said the congressman has reservations about the Frank bill because it is too expensive and does not clearly spell out how the money is to be used. ``Joe just feels there's a better bill out there,'' said Chuck McDermott, a Kennedy aide, adding that Kennedy also supports other measures that would provide for construction and rehabilitation of public housing.