A compromise welfare bill that would cost $8 billion a year above the existing program, compared with $20 billion for President Carter's proposal, is being prepared by Senate minority Leader Howard H. Baker (R-Tenn.); Sen. Abraham A. Ribicoff (D-Conn.), a former secretary of health, education and welfare; Senate Budget Committee senior Republican Henry L. Bellmon (Okla), and Sen. John C. Danforth (R-Mo.).

The bill wouldn't bring low-income single persons and childless couples under the welfare programs, as would the house welfare subcommittee version of the Carter measure, nor would it create as many new public service jobs for welfare recipients, or automatically "cash out" food stamps.

The key features:

Low-income families with unemployed fathers would be eligible for welfare all over the country, instead of only in 26 states, if there were children in the family. A floor of 60 percent of the poverty level in income would be guaranteed.The floor would work out to $4,600 for a family of four in 1982, consisting of cash and food stamps.

Private and nonprofit employers would receive a U.S. subsidy of $1 an hour for employing welfare recipients, long-term unemployed persons and unemployed youths, provided they didn't displace existing jobholders.

Private employers could opt alternatively for a $1-an-hour tax credit.

As many as 375,000 public service jobs would be created in 1982 for welfare recipients unable to find work.