Yes, there is a condition. We say faith, but God heals faithfully even the sinner, He infact came to save them. So He is not limited to anything in way of His will in any purpose He decides in way of healing. But we also know that God says, you have not because you ask not. Prayer is a requirement in things and He states a condition or a description of faith when He says, "If you remain in Me and My Word remains in you ask whatever you wish and it will be given you." So the description or condition of faith is that we surrender to God. Then there is the will or purpose of God in way of your understanding vs. His on each matter. He says He will answer your prayers. We conclude that always means the preverbal "Yes". But of coarse there are three options to be sure: 'Yes', 'No', and 'Maybe'. We tend to look at the healing in a specific way always, yet God, altho interested in the specifics of healing also sees the bigger picture to need. That's His jurisdiction not ours for it is He that is all-knowing not us.
God also talks about another condition: "seek ye with all your strength." So we too need to not stop asking, even Fasting, faithfully believing He has not left us high and dry, For He has not. We can ask also why did the disciples go down the street and heal everyone along the way? Well, some of our facts need to be examined to the accuracy of everyone, for they did not heal everyone. But this was also God's will at the time to show of Jesus and His power. Does His healing lack any less power today? NO! But His will and purpose of healing now is in His wheel-house not ours, outside of our prayers that move God toward it. Prayer is huge, the person or thing prayed over need not comply to God for God to move in favor of it, it is the power of your prayer that moves the Holy Spirit to pray to God with you toward this person or healing or event etc.
Bottom line do we pursue God's healing as if it is so? Or do we pursue God in lew of our need based on fear of it not being so? Jesus says He is the Way, the Truth, and the Life. The way then to healing is thru Him!