That ye receive her in the Lord, as becometh saints, and that ye assist her in whatsoever business she hath need of you: for she hath been a succourer of many, and of myself also.
Note 3 at Ro 16:2: One definition of the word "for" is "because; since" (American Heritage Dictionary). Paul was saying that the reason they should assist Phebe is because she had assisted others, including Paul. This illustrates the law of reaping what you sow (Ga 6:7 and Lu 6:38).
Some people become offended when they do not receive assistance from others, yet they have never helped anyone. That is not what Paul was advocating here. Phebe had earned their help. Salvation is by grace, but respect and help from others has to be earned.