What bike is recommended? My car broke down 2 weeks ago so I bought a used bike off offer up so I can commute to work 8.30 miles there and another 8 back (50 min ride) I bought a used Avalon and it worked fine for 2 weeks. The gears started to fail the chain would come off. A few days ago the front wheel started to wobble and today I got a flat. I am looking to purchase a bike and would love to hear your thoughts. I don't know what to get. I only have $200 to spend &amp; I need it by tomorrow. I don't ride the bike on the street I ride it on the sidewalk but there are some areas where I have to ride it on grass/rocky dirt areas. I also have to tackle 3 hills. 
P.s  I am. 5''4 and weight 230lbs
Use a local bike shop (LBS) who can give you good advice and proper servicing.

Don't be tempted to get a big that is too big for you; reach is more important than height. I often see people over stretched. Also go for a bike that is well built rather than a Walmart 'bargain'.

Good bikes last for years and years and are fixable. Modern bikes with decent wheels and brakes are often cheaper than buying an old boneshaker. Spend the extra for reliability and make sure you get a decent lock so it isn't stolen the first time you turn your back.

Keep you tires properly inflated (60 psi minimum) and take advantage of your LBS's track pump for a top up every 2 weeks or so.