Lag was certainly a problem where I couldn't shoot the enemies before I somehow managed to bump into them to where I felt like I had no control over the character at all. Also a bit of sound design to signify increase of money and loss of health would help.

It's a good start – and please continue working on it – but I have several issues with the game as it works right now. The major ones:

– The perspective is weird. It's top-down, but your collision box is flat, not just at your feet. Therefore you keep getting hit by missiles which should logically go around you, you bump your head into traffic cones if you walk too close.
– The worst offender of the above is the hospital: bumping your head into its *wall* immediately makes you enter and deducts $20. There's no confirmation screen, the interior is simply a transparent void, and you can still lose money even at full health.
– Leaving a building puts you in the middle of the road, instead of in front of the building.
– At first, I didn't understand the screen loops, and because you're standing on a road, I thought I'm supposed to explore the surroundings. That's not the case.
– The shops are the first things you see, before you even know what you're dealing with, before you even know what you're supposed to be doing. You should make it so the player at least encounters an enemy before they can reach the shop for the first time.
– It really does lag, especially when you walk onto a different terrain for the first time. What happens there? Perhaps there's some loading which can be optimised by loading gradually or in the background, instead of all at once.
– Enemies are somewhat optional. You encounter them at two exact locations, and they don't spawn unless you're nearby. They immediately walk away (which is great because you can't just stand and keep shooting them) and continue to chase after you, but you can just walk into the shop if you get in trouble and leave.
– Shooting enemies is a hassle. They shoot your oversized hitbox with perfect precision, but you have to position yourself perfectly to shoot them. If they miss, they just walk into you, and they can also come in groups and shoot barrages of bullets at once. It becomes very chaotic very quickly and you can't reasonably defend yourself.
– What's the goal? What do you achieve? Is there a victory condition, a sense of progression?

There are some minor issues to talk about, too (e.g. the position of your feet shouldn't change when you simply change the direction), but focusing on fine-tuning the details is unimportant when there are more glaring issues.

All in all, the main problem is that the game – the core gameplay – isn't all that enjoyable; at least for me.
Take a step back (put aside cash, ammo, upgradeable equipment) and consider what should be the one gameplay element to stay if you had to remove everything else. Or describe the game in one sentence ("It's a game about (…).").
"Shooting enemies, dodging bullets" might be an answer; in such case make sure shooting enemies is enjoyable, not frustrating (e.g. shoot with the mouse, make bullets larger, slow down enemies etc.) and you can actually dodge incoming bullets (limit the number of enemies, make the bullets slower). You could also spawn enemies from all sides of the map, not just from two spawn points, to make it less predictable.
But it's up to you – I'm just listing what might be viable options, but you might find out something works much better.

I hope that helped. It's a very good start, but the core design needs some tweaking.