Realistically you are looking at five years before any approval. The chance of success is <8% (on average).

The median phase III trial in their data set cost $21.4 million, they reported last year in Nature Reviews Drug Discovery. The median phase II trial cost $8.6 million, and the median phase I trial cost $3.4 million, they also reported.

https://www.nature.com/articles/nrd.2018.198

From the FDA

Step 3: Clinical Research

Phase 2

Study Participants:Up to several hundred people with the disease/condition.

Length of Study: Several months to 2 years

Purpose: Efficacy and side effects

Approximately 33% of drugs move to the next phase

Phase 3

Study Participants:300 to 3,000 volunteers who have the disease or condition

Length of Study: 1 to 4 years

Purpose: Efficacy and monitoring of adverse reactions

Approximately 25-30% of drugs move to the next phase

https://www.fda.gov/patients/drug-development-process/step-3-clinical-research