Salvation comes in a moment. When a person believes in Jesus, he is eternally saved. (Acts.)
“Obeying God” can mean believing His Gospel.
“Believe in Jesus” is a command that God wants you to obey. It has nothing to do with “easy believism.” Salvation (meaning “going to Heaven when you die”) is a FREE GIFT.
What is difficult is ~discipleship~. Discipleship is NOT a condition of salvation. If it were, then salvation would be achieved by your own good works.